Publications

Arpad Pasztor, Alessandro Scarfato, Marcello Spera, Felix Flicker, Céline Barreteau, Enrico Giannini, Jasper van Wezel and Christoph Renner

Nature communications 12 1, 6037 (2021)

In the presence of multiple bands, well-known electronic instabilities may acquire new complexity. While multiband superconductivity is the subject of extensive studies, the possibility of multiband charge density waves (CDWs) has been largely ignored so far. Here, combining energy dependent…

Jean-Marie Poumirol, Adrien Bercher, Tetiana Slipchenko, Ivan Maggio-Aprile, Christoph Renner and Alexey Kuzmenko

Physical review applied 16 4, 044012 (2021)

We present a very-compact bicomponent-permanent-magnet design capable of generating 1.25 T in a small volume, significantly above the 0.6 T available from a single uniformly magnetized permanent magnet. In addition to the enhanced maximum field, our design drastically limits the stray field present …

A. P. Petrović, M. Raju, X. Y. Tee, A. Louat, Ivan Maggio-Aprile, R. M. Menezes, M. J. Wyszyński, N. K. Duong, M. Reznikov, Christoph Renner, M. V. Milošević and C. Panagopoulos

Physical Review Letters 126 117205 (2021)

We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ≈50 nm is sufficient to nucleate antivortices in a 25 nm Nb film, with unique signatures in the magnetization, critical current, and flux dynamics, …

Tim Gazdic, Ivan Maggio-Aprile, Genda Gu and Christoph Renner

Physical Review X 11, 031040 (2021)

Low magnetic field scanning tunneling spectroscopy of individual Abrikosov vortices in heavily overdoped Bi2Sr2CaCu2O8+δ unveils a clear d-wave electronic structure of the vortex core, with a zero-bias conductance peak at the vortex center that splits with increasing distance from the core. We…

Tim Gazdic

Thèse (2020)

We study high temperature superconductivity of heavily overdoped (p~0.22) Bi2Sr2CaCu2O8+d with the objective to find signatures of the more conventional superconductivity anticipated in comparison to its more widely studied underdoped counterpart. We find some similarities as well as distinctly…

Marcello Spera, Alessandro Scarfato, Arpad Pasztor, Enrico Giannini, D. R. Bowler and Christoph Renner

Physical Review Letters 125 267603 (2020)

Charge density waves (CDWs) are understood in great detail in one dimension, but they remain largely enigmatic in two-dimensional systems. In particular, numerous aspects of the associated energy gap and the formation mechanism are not fully understood. Two long-standing riddles are the amplitude…

Marcello Spera, Alessandro Scarfato, Enrico Giannini and Christoph Renner

Physical Review. B, Condensed Matter 99 155133, 1-7 (2019)

We report a detailed study of the microscopic effects of Cu intercalation on the charge density wave (CDW) in 1T-CuxTiSe2. Scanning tunneling microscopy and spectroscopy reveal a unique, Cu-driven spatial texturing of the charge-ordered phase, with the appearance of energy-dependent CDW patches and …

Marcello Spera

Thèse (2019)

In this work, we performed a detailed scanning tunnelling microscopy and spectroscopy study of the charge density wave state of 1T-CuxTiSe2 in a wide range of Cu concentrations (0 < x < 0.07), an apparently perfect playground for investigating the interplay between correlated ground states. Thanks...

Renan Villarreal, Christopher J. Kirkham, Alessandro Scarfato, David R. Bowler and Christoph Renner

Journal of Applied Physics 125 18, 184301 (2019)

The surface diffusion potential landscape plays an essential role in a number of physical and chemical processes such as self-assembly and catalysis. Diffusion energy barriers can be calculated theoretically for simple systems, but there is currently no experimental technique to systematically…

Arpad Pasztor, Alessandro Scarfato, Marcello Spera, Céline Barreteau, Enrico Giannini and Christoph Renner

Physical Review Research 1 3, 033114 (2019)

The charge density wave (CDW) in solids is a collective ground state combining lattice distortions and charge ordering. It is defined by a complex order parameter with an amplitude and a phase. The amplitude and wavelength of the charge modulation are readily accessible to experiment. However,…

Arpad Pasztor

Thèse (2018)

The charge density wave (CDW) phase in bulk and exfoliated crystals of transition metal dichalcogenides was studied by scanning tunneling microscopy (STM). In exfoliated flakes of VSe2 we found a striking non-monotonic evolution of the CDW transition temperature as function of thickness derived…

José Martinez Castro, Diego Mauro, Arpad Pasztor, Ignacio Gutierrez Lezama, Alessandro Scarfato, Alberto Morpurgo and Christoph Renner

Nano Letters 18 11, 6696-6702 (2018)

Many atomically thin exfoliated two-dimensional (2D) materials degrade when exposed to ambient conditions. They can be protected and investigated by means of transport and optical measurements if they are encapsulated between chemically inert single layers in the controlled atmosphere of a…

Evgeniy Ponomarev, Arpad Pasztor, Adrien Waelchli, Alessandro Scarfato, Nicolas Ubrig, Christoph Renner and Alberto Morpurgo

ACS Nano (2018)

Arpad Pasztor, Alessandro Scarfato and Christoph Renner

Review of scientific instruments 88 7, 076104 (2017)

Exfoliation, namely, the peeling of layered materials down to a single unit-cell thin foil, opens promising avenues to fabricate novel electronic materials. New properties and original functionalities emerge in the single and few layer configurations of a number of layered compounds, in particular…

Renan Villarreal

Thèse (2017)

Manganese self-assembles into atomic chains on the Si(001) reconstructed surface. Our combined scanning tunneling microscopy, atomic force microscopy (AFM) and density functional theory (DFT) study revealed a simple necklace-like structure of the Mn chains. The DFT calculated adsorption energies…

C. J. Kirkham, Maria Longobardi, Sigrun Antje Koester, Christoph Renner and D. R. Bowler

Physical review. B, Condensed matter and materials physics 96 7, 075304 (2017)

Scanning tunneling microscopy (STM) reveals unusual sharp features in otherwise defect-free Bi nanolines self-assembled on Si(001). They appear as subatomic thin lines perpendicular to the Bi nanoline at positive biases and as atomic size beads at negative biases. Density functional theory (DFT)…

M. Longobardi, C. J. Kirkham, Renan Villarreal, Sigrun Antje Koester, D. R. Bowler and Christoph Renner

Physical Review. B, Condensed Matter 96 23, 235421 (2017)

Atomic nanolines are one-dimensional systems realized by assembling many atoms on a substrate into long arrays. The electronic properties of the nanolines depend on those of the substrate. Here, we demonstrate that to fully understand the electronic properties of Bi nanolines on clean Si(001)…

Anna Maria Novello, Marcello Spera, Alessandro Scarfato, Alberto Ubaldini, Enrico Giannini, D. R. Bowler and Christoph Renner

Physical review letters 118 1, 017002 (2017)

We study the impact of Cu intercalation on the charge density wave (CDW) in 1T-CuxTiSe2 by scanning tunneling microscopy and spectroscopy. Cu atoms, identified through density functional theory modeling, are found to intercalate randomly on the octahedral site in the van der Waals gap and to dope…

Arpad Pasztor, Alessandro Scarfato, Céline Barreteau, Enrico Giannini and Christoph Renner

2D Materials 4 4, 041005 (2017)

Isolating single unit-cell thin layers from the bulk matrix of layered compounds offers tremendous opportunities to design novel functional electronic materials. However, a comprehensive thickness dependence study is paramount to harness the electronic properties of such atomic foils and their…

Christophe Berthod, Ivan Maggio-Aprile, Jens Erik Bruer, Andréas Erb and Christoph Renner

Physical Review Letters 119 23, 237001 (2017)

The copper oxides present the highest superconducting temperature and properties at odds with other compounds, suggestive of a fundamentally different superconductivity. In particular, the Abrikosov vortices fail to exhibit localized states expected and observed in all clean superconductors. We…

Jens Erik Bruer, Ivan Maggio-Aprile, Nathan Jenkins, Zoran Ristic, Andréas Erb, Christophe Berthod, Oystein Fischer and Christoph Renner

Nature communications 7 11139 (2016)

The observation by scanning tunnelling spectroscopy (STS) of Abrikosov vortex cores in the high-temperature superconductor YBa$_2$Cu$_3$O$_{7-delta}$ (Y123) has revealed a robust pair of electron-hole symmetric states at finite subgap energy. Their interpretation remains an open question because…

Thomas Amundsen

Thèse (2016)

We present a scanning tunnelling microscopy study of the metal insulator (MI) phase transition in NdNiO3 thin films grown on NdGaO3. Although topographic resolution is limited to grain structures and step edges, we did achieve high resolution and reproducible spectroscopic mapping of the thin film…

Anna Maria Novello

Thèse (2015)

The interplay between charge order and superconductivity has been a long standing puzzle in a wide range of superconducting materials. The transition metal dichalcogenide 1T-TiSe2 is an interesting material that can give an important contribution to this debate. Indeed, 1T-TiSe2 undergoes a charge…

Anna Maria Novello, B. Hildebrand, Alessandro Scarfato, C. Didiot, G. Monney, Alberto Ubaldini, H. Berger, D. R. Bowler, P. Aebi and Christoph Renner

Physical review. B, Condensed matter and materials physics 92 8, 081101 (2015)

We present a detailed low-temperature scanning tunneling microscopy (STM) study of the commensurate charge densitywave(CDW) in 1T -TiSe2 in the presence of single atomdefects.Wefindno significant modification of the CDWlattice in single crystals with native defect concentrations where some bulk…

Renan Villarreal, Maria Longobardi, S. A. Köster, Ch. J. Kirkham, D. Bowler and Christoph Renner

Physical review letters 115 25, 256104 (2015)

Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural…

Didier Perret, Hans-Rudolf Hagemann, Radovan Cerny, Christoph Renner, Enrico Giannini, Laure Guenee, Céline Besnard, David Gerard and Lionel Windels

Chimia 68 12, 893-895 (2014)

To celebrate the International Year of Crystallography among the general public, a consortium of chemists, physicists and crystallographers of the University of Geneva organised in Spring 2014 an incentive crystal growth contest for Geneva scholars aged 4 to 19. Starting from a kit containing a…

Ignacio Gutierrez Lezama, Alberto Ubaldini, Maria Longobardi, Enrico Giannini, Christoph Renner, Alexey Kuzmenko and Alberto Morpurgo

2D materials 1 2, 021002 (2014)

Semiconducting transition metal dichalcogenides (TMDs) have emerged as materials that can be used to realize two-dimensional (2D) crystals possessing rather unique transport and optical properties. Most research has so far focused on sulfur and selenium compounds, while tellurium-based materials…

Jens Erik Bruer

Thèse (2014)

The mechanism underlying high temperature superconductivity continues to challenge our understanding. Scanning tunneling spectroscopy (STM) has historically been one of the prime techniques to tackle superconductivity in conventional BCS materials, providing key insight into the pairing mechanism….

B. Hildebrand, C. Didiot, Anna Maria Novello, G. Monney, Alessandro Scarfato, Alberto Ubaldini, H. Berger, D. R. Bowler, Christoph Renner and P. Aebi

Physical review letters 112 19, 197001 (2014)

The transition-metal dichalcogenide 1T-TiSe2 is a quasi-two-dimensional layered material with a charge density wave (CDW) transition temperature of TCDW ≈ 200 K. Self-doping effects for crystals grown at different temperatures introduce structural defects, modify the temperature-dependent…

F. Bobba, C. Di Giorgio, Alessandro Scarfato, Maria Longobardi, M. Iavarone, S. A. Moore, G. Karapetrov, V. Novosad, V. Yefremenko and A. M. Cucolo

Physical review. B, Condensed matter and materials physics 89 21, 214502 (2014)

Low-temperature magnetic force microscopy was used to study the threshold of nucleation of spontaneous vortex-antivortex structures in superconductor/ferromagnet (S/F) hybrid systems. We investigated S/F heterostructures composed of Py as the magnetic material and Nb as the superconductor, with…

François Bianco, Sigrun Antje Koester, Maria Longobardi, James Owen, D. R. Bowler and Christoph Renner

AIP conference proceedings 1566, 409-410 (2013)

We present a detailed study of the structural and electronic properties of a self-assembled silicon nanoline embedded in the monohydride Si(001):H surface, known as the Haiku stripe. The nanoline is a perfectly straight and defect free endotaxial structure of huge aspect ratio; it can grow…

K. Iwaya, D. R. Bowler, V. Brázdová, A. Ferreira da Silva, Christoph Renner, W. Wu, A. J. Fisher, A. M. Stoneham and G. Aeppli

Physical review. B, Condensed matter and materials physics 88 3 (2013)

The determining factor of the bulk properties of doped Si is the column rather than the row in the periodic table from which the dopants are drawn. It is unknown whether the basic properties of dopants at surfaces and interfaces, steadily growing in importance as microelectronic devices shrink, are …

Quy Khac Ong, Javier Reguera, Paulo Jacob Silva, Mauro Moglianetti, Kellen Harkness, Maria Longobardi, Kunal S. Mali, Christoph Renner, Steven De Feyter and Francesco Stellacci

ACS nano 7 10, 8529-8539 (2013)

Gold nanoparticles protected by a binary mixture of thiolate molecules have a ligand shell that can spontaneously separate into nanoscale domains. Complex morphologies arise in such ligand shells, including striped, patchy, and Janus domains. Characterization of these morphologies remains a…

Fabio Biscarini, Quy Khac Ong, Cristiano Albonetti, Fabiola Liscio, Maria Longobardi, Kunal S. Mali, Artur Ciesielski, Javier Reguera, Christoph Renner, Steven De Feyter, Paolo Samorì and Francesco Stellacci

Langmuir 29 45, 13723-13734 (2013)

Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by scanning tunneling microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images…

François Bianco, David R. Bowler, James Owen, Sigrun Antje Koester, Maria Longobardi and Christoph Renner

ACS nano 7 5, 4422-4428 (2013)

Silicon dangling bonds exposed on the monohydride silicon (001) (Si(001):H) surface are highly reactive, thus enabling site-selective absorption of atoms, and single molecules into custom patterns designed through the controlled removal of hydrogen atoms. Current implementations of high-resolution…

François Bianco

Thèse (2013)

Dans ce travail, nous nous sommes intéressé à l’auto assemblage de nanolignes de bismuth sur la surface du silicium et des structures dérivées de ces nanolignes. Nous avons découvert que l’hydrogénation permet d’enlever complètement le bismuth de la surface tout en conservant la…

H. J. Liu, James Owen and K. Miki

Journal of physics. Condensed matter 24 9, 095005 (2012)

Higher manganese silicide nanowires have been grown on the Si(001)-2 × 1 surface by the pre-growth of Bi nanolines. Scanning tunnelling microscope (STM) observations show that the nanowire has a linear surface reconstruction with a periodicity of 0.56 nm, and we propose a reconstruction on their…

J.S. Milne, I. Favorskiy, A.C.H. Rowe, S. Arscott and Christoph Renner

Physical review letters 108 25, 5 p. (2012)

The room-temperature longitudinal piezoresistance of n-type and p-type crystalline silicon along selected crystal axes is investigated under uniaxial compressive stresses up to 3 GPa. While the conductance (G) of n-type silicon eventually saturates at about 45% of its zero-stress value (G0) in…

B. Bryant, Christoph Renner, Y. Tokunaga, Y. Tokura and G. Aeppli

Nature communications 2, 212 (2011)

Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes; they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked…

François Bianco, James Owen, Sigrun Antje Koester, Daniel Mazur, Christoph Renner and D. Bowler

Physical review. B, Condensed matter and materials physics 84 3 (2011)

We present a detailed study of the structural and electronic properties of a self-assembled silicon nanoline embedded in the H-terminated silicon (001) surface, known as the Haiku stripe. The nanoline is a perfectly straight and defect-free endotaxial structure of huge aspect ratio; it can grow…

H J Liu, James Owen, K Miki and Christoph Renner

Journal of physics. Condensed matter 23 17, 172001 (2011)

A method for promoting the growth of manganese silicide nanowires on Si(001) at 450 °C is described. The anisotropic surface stress generated by bismuth nanolines blocks the formation of embedded structures and stabilizes the nucleation of manganese silicide islands which grow in a preferred…

K.C. Rahnejat, C.A. Howard, N.E. Shuttleworth, S.R. Schofield, K. Iwaya, C.F. Hirjibehedin, Christoph Renner, G. Aeppli and M. Ellerby

Nature communications 2, 558 (2011)

Graphitic systems have an electronic structure that can be readily manipulated through electrostatic or chemical doping, resulting in a rich variety of electronic ground states. Here we report the first observation and characterization of electronic stripes in the highly electron-doped graphitic…

James Owen, François Bianco, S. Köster, Daniel Mazur, D. R. Bowler and Christoph Renner

Applied physics letters 97 9, 093102 (2010)

Single atom metallic wires of arbitrary length are of immense technological and scientific interest. We present atomic-resolution scanning tunneling microscope data of a silicon-only template, which modeling predicts to enable the self-organized growth of isolated micrometer long surface and…

Jakub Javorský, James Owen, Martin Setvín and Kazushi Miki

Journal of physics. Condensed matter 22 17, 175006 (2010)

By means of scanning tunnelling microscopy and spectroscopy, we have investigated the electronic structure of Bi nanolines on clean and H-passivated Si(100) surfaces. Maps of the local density of states (LDOS) images of the Bi nanolines are presented for the first time. The spectra obtained for…

J.S. Milne, A.C.H. Rowe, S. Arscott and Christoph Renner

Physical review letters 105 22, 4 p. (2010)

The giant piezoresistance (PZR) previously reported in silicon nanowires is experimentally investigated in a large number of depleted silicon nano- and microstructures. The resistance is shown to vary strongly with time due to electron and hole trapping at the sample surfaces independent of the…

James Owen

Journal of physics. Condensed matter 21 44, 443001 (2009)

Ammonia is a good model system for the study of co-adsorption interactions, including indirect effects such as charge and strain-induced local effects on adsorption sites, and direct interactions such as hydrogen bonding. On the Si(001) surface, it adsorbs molecularly, via a dative bond from the N…

James Owen and D. R. Bowler

Surface science 603 18, 2902-2906 (2009)

We discuss the interaction between adsorbing ammonia molecules and pre-adsorbed ammonia fragments on the Si(001) surface, searching for experimental evidence of a H-bonded precursor state predicted by modelling. While correlations along dimer rows have already been identified, these mix…

Christoph Renner

Nature materials 8 4, 245-247 (2009)

To counter the decreasing interest in scientific studies, the PhysiScope at the University of Geneva conveys scientific excitement to teenagers by offering an entertaining and practical way to discover physics.

A.C.H. Rowe, Christoph Renner and S. Arscott

TRANSDUCERS 2009 – 2009 International Solid-State Sensors, Actuators and Microsystems Conference (2009)

We demonstrate here a simple planar aluminium-silicon strain sensor incorporating an external aluminium ohmic shunt (metal-semiconductor hybrid) which exhibits a geometrically enhanced room-temperature gauge factor (GF) of up to 843 under uni-axial tensile strains of up of 8 times 10 -5 for a…

A. C. H. Rowe, A. Donoso-Barrera, Christoph Renner and S. Arscott

Physical review letters 100 14 (2008)

Metal-semiconductor hybrids are artificially created structures presenting novel properties not exhibited by either of the component materials alone. Here we present a giant piezoresistance effect in a hybrid formed from silicon and aluminum. The maximum piezoresistive gage factor of 843, measured…

James Owen and D. R. Bowler

Surface science 602 24, 3760-3762 (2008)

In their paper, Chung et al. [O.N. Chung, H. Kim, J.-Y. Koo, S. Chung, Surf. Sci. Lett. 602 (2008) L69.] discuss the interaction of adsorbing ammonia fragments on the Si(0 0 1) surface. We suggest that they have failed adequately to explain the correlations they observe. Using a different…

Silvia Santis, Benjamin Bryant, Marc Warner, Hai Wang, Tsuyoshi Kimura, Yoshinori Tokura, Christoph Renner, Antonio Bianconi and Gabriel Aeppli

Journal of superconductivity and novel magnetism 20 7-8, 531-533 (2007)

We report scanning tunnelling microscopy images of polaronic charge ordered patch on the layered ferromagnet La2−2x Sr1+2x Mn2O7, x=0.32. The spectroscopic investigation shows that the material is gapped above and below the critical temperature, where the gap changes from 500 to 800 mV, giving…

Sandrine Heutz, Chiranjib Mitra, Wei Wu, Andrew J. Fisher, Andrew Kerridge, Marshall Stoneham, Tony  H. Harker, Julie Gardener, Hsiang-Han Tseng, Tim S. Jones, Christoph Renner and Gabriel Aeppli

Advanced materials 19 21, 3618-3622 (2007)

The design and fabrication of materials that exhibit both semiconducting and magnetic properties for spintronics and quantum computing has proven difficult. Important starting points are high-purity thin films as well as fundamental theoretical understanding of the magnetism. Here we show that…

Oystein Fischer, Martin Kugler, Ivan Maggio-Aprile, Christophe Berthod and Christoph Renner

Reviews of modern physics 79 1, 353 (2007)

Tunneling spectroscopy has played a central role in the experimental verification of the microscopic theory of superconductivity in classical superconductors. Initial attempts to apply the same approach to high-temperature superconductors were hampered by various problems related to the complexity…

A M Stoneham, J Gavartin, A L Shluger, A V Kimmel, D Muñoz Ramo, H M Rønnow, G Aeppli and Christoph Renner

Journal of Physics. Condensed Matter 19 255208 (2007)

The earliest ideas of the polaron recognized that the coupling of an electron to ionic vibrations would affect its apparent mass and could effectively immobilize the carrier (self-trapping). We discuss how these basic ideas have been generalized to recognize new materials and new phenomena. First,…

F Loviat, H M Rønnow, Christoph Renner, G Aeppli, T Kimura and Y Tokura

Nanotechnology 18 044020 (2007)

Recently, several informative reports have been published on spectroscopy experiments performed on cleaved surfaces of the bilayered colossal magnetoresistive manganite La2−2x Sr1+2x Mn2O7 (Konoto et al 2004Phys. Rev. Lett. 93 107201, Freeland et al 2005 Nat. Mater. 4 62, Mannella et al 2005…

Christoph Renner and Henrik M. Rønnow

Scanning Probe Microscopy, 534-558 (2007)

H. M. Rønnow, Christoph Renner, G. Aeppli, T. Kimura and Y. Tokura

Nature 440 7087, 1025-1028 (2006)

A remarkable feature of layered transition-metal oxides—most famously, the high-temperature superconductors—is that they can display hugely anisotropic electrical and optical properties (for example, seeming to be insulating perpendicular to the layers and metallic within them), even when…

G. Aeppli, P. Warburton and Christoph Renner

BT Technology Journal 24 3, 163-169 (2006)

There is a clear imperative to continue the IT revolution, even in the face of limits both from the laws of physics, as well as the challenge of managing complexity. Beyond changing the nature of hardware itself, nanotechnology and the replacement of classical logic gates with devices exploiting…

Christoph Renner, G. Aeppli and H.M. Ronnow

Materials Science and Engineering. C 25 5-8, 775-778 (2005)

A microscopic characterisation of the phase transitions associated with colossal magnetoresistance (CMR) in manganese perovskite oxides is a very important ingredient in the quest of understanding its underlying mechanism. Scanning tunneling microscopy (STM) is most suitable to investigate some of…

A M Stoneham, G Aeppli, P Bayvel, I Boyd, A J Fisher, P T Greenland, A H Harker and Christoph Renner

Actes de conférence (2003)

Bart Wiebren Hoogenboom, Christoph Renner, Ivan Maggio-Aprile and Oystein Fischer

Vortices in Unconventional Superconductors and Superfluids, 269-282 (2002)

Oystein Fischer, Christoph Renner and Ivan Maggio-Aprile

The Gap Symmetry and Fluctuations in High-Tc Superconductors (2002)

Christoph Renner, G. Aeppli, B.-G. Kim, Yeong-Ah Soh and S.-W. Cheong

Nature 416 6880, 518-521 (2002)

Transition-metal perovskite oxides exhibit a wide range of extraordinary but imperfectly understood phenomena. The best known examples are high-temperature superconductivity in copper oxides(1), and colossal magnetoresistance in manganese oxides (‘manganites’)(2,3). All of these materials undergo a …

Bart Wiebren Hoogenboom, K. Kadowaki, Bernard Revaz, M. Li, Christoph Renner and Oystein Fischer

Physical review letters 87 26 (2001)

We present a scanning tunneling spectroscopy study on quasiparticle states in vortex cores in Bi2Sr2CaCu2O8+δ. The energy of the observed vortex core states shows an approximately linear scaling with the superconducting gap in the region just outside the core. This clearly distinguishes them from…

Martin Kugler, Oystein Fischer, Christoph Renner, S. Ono and Yoichi Ando

Physical review letters 86 21, 4911-4914 (2001)

Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi2Sr2CuO6+δ between 275 mK and 82 K. Below Tc=10K, the spectra show a gap with well-defined coherence peaks at ±Δp≃12meV, which disappear at Tc. Above Tc, the…

Olivier Kuffer, Ivan Maggio-Aprile, Jean-Marc Triscone, Oystein Fischer and Christoph Renner

Applied physics letters 77 11, 1701 (2000)

We report on scanning tunneling microscopymeasurements of the piezoelectric response in ferroelectricheterostructuresgrown by off-axis rf magnetronsputtering. The samples are composed of a single-crystalline ferroelectricfilm of Pb(Zr0.2Ti0.8)O3deposited on a conducting substrate and covered with…

Martin Kugler, Christoph Renner, V. Mikheev, G Batey and Oystein Fischer

Physica. B, Condensed matter 280 1-4, 551-552 (2000)

We present a scanning tunneling microscope (STM) operating between 275 mK and room temperature in ultra-high vacuum (UHV) and in magnetic fields up to 14 T. The system features a compact STM fixed to a UHV compatible 3He insert fitting into a bottom loading cryostat with a superconducting magnet….

Bart Wiebren Hoogenboom, Christoph Renner, Bernard Revaz, Ivan Maggio-Aprile and Oystein Fischer

Physica. C, Superconductivity 332 1-4, 440-444 (2000)

Scanning tunneling spectroscopy allows us to study the changes in the quasiparticle local density of states due to the presence of vortex cores in Bi2Sr2CaCu2O8+δ (BSCCO). The vortex core spectra are characterized by a gap-like structure similar to the pseudogap measured above Tc. We also observe…

Bart Wiebren Hoogenboom, Martin Kugler, Bernard Revaz, Ivan Maggio-Aprile, Oystein Fischer and Christoph Renner

Physical review. B, Condensed matter and materials physics 62 13, 9179-9185 (2000)

We present a detailed study on the behavior of vortex cores in Bi2Sr2CaCu2O8+δ using scanning tunneling spectroscopy. The very irregular distribution and shape of the vortex cores imply a strong pinning of the vortices by defects and inhomogeneities. The observed vortex cores seem to consist of…

Martin Kugler, Christoph Renner, Oystein Fischer, V. Mikheev and G. Batey

Review of Scientific Instruments 71 3, 1475-1478 (2000)

We present a scanning tunneling microscope (STM) designed to operate between 275 mK and room temperature, in magnetic fields up to 14 T and in ultrahigh vacuum (UHV). The system features a compact STM connected to an UHV compatible He-3 refrigerator fitting into a bottom loading cryostat with a…

Ivan Maggio-Aprile, Christoph Renner, Andréas Erb, Eric Walker, Bernard Revaz, Jean-Yves Genoud, Kazuo Kadowaki and Oystein Fischer

Journal of Electron Spectroscopy and Related Phenomena 109 1-2, 147-155 (2000)

During past years, scanning tunneling spectroscopy (STS) investigations of high temperature superconductors have revealed unusual characteristics of the superconducting gap. We present here the temperature dependence of the tunneling conductance spectra on YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+delta…

Christoph Renner, Bernard Revaz, Kazuo Kadowaki, Ivan Maggio-Aprile, Andréas Erb, Eric Walker and Oystein Fischer

Advances in Superconductivity XI : Proceedings of the 11th International Symposium on Superconductivity (ISS’98), 145-150 (1999)

We present scanning tunneling spectroscopy (STS) investigations of high temperature superconductors illustrating the very unusual characteristics of the superconducting gap, and the intimate relation existing between the superconducting and the normal-state gap (pseudogap). A unique feature of STS…

Alain Junod, Andréas Erb and Christoph Renner

Physica C: Superconductivity and Its Applications 317-318, 333-344 (1999)

We consider the experimental trends in a database of specific heat measurements near T-c in high magnetic fields for type-II superconductors with a large value of kappa = lambda/xi, including mostly high-temperature superconductors. Whereas the BCS limiting case is well established in low-T-c…

Christoph Renner, Bernard Revaz, Jean-Yves Genoud, K. Kadowaki and Oystein Fischer

Physical Review Letters 82 18, 3726 (1999)

Christoph Renner, Ivan Maggio-Aprile and Oystein Fischer

The Superconducting State in Magnetic Fields: Special Topics and New Trends, 226-244 (1998)

Christoph Renner, Bernard Revaz, Jean-Yves Genoud, K. Kadowaki and Oystein Fischer

Physical Review Letters 80 1, 149-152 (1998)

We present tunneling spectroscopy of Bi2Sr2CaCU2O8+delta Single crystals as a function of oxygen doping and temperature. The doping dependence amounts essentially to an energy scaling of the tunneling spectra, with a quasiparticle gap that is reduced with increasing oxygen concentration. This…

Christoph Renner, Bernard Revaz, K. Kadowaki, Ivan Maggio-Aprile and Oystein Fischer

Physical Review Letters 80 16, 3606-3609 (1998)

Vortex cores in under- and overdoped Bi2Sr2CaCu2O81d are studied by local probe tunneling spectroscopy. At the center of the cores, we find a gaplike structure at the Fermi level which scales with the superconducting gap, but no quasiparticle bound states. This low temperature pseudogap is…

Christoph Renner, Ivan Maggio-Aprile and Oystein Fischer

Physikalische Blätter 54 5, 427-430 (1998)

Ivan Maggio-Aprile, Christoph Renner, Andréas Erb, Eric Walker and Oystein Fischer

Nature 390 6659, 487-490 (1997)

Interest in vortex matter has risen considerably since the discovery of the high-temperature superconductors, which exhibit magnetic vortex states that are especially rich and complex(1). The global behaviour of magnetic vortices in nearly perfect crystals-such as melting of the vortex…

Oystein Fischer, Christoph Renner, Ivan Maggio-Aprile, Andréas Erb, Eric Walker, Bernard Revaz and Jean-Yves Genoud

Physica C: Superconductivity and Its Applications 282-287, 315-318 (1997)

We report scanning tunneling spectroscopy investigations on the doping and temperature dependence of the tunneling spectra on Bi2Sr2CaCu2O8+δ, and on the vortex lattice observation on YBa2Cu3O7−δ.

Christoph Renner, Ivan Maggio-Aprile, Andréas Erb, Eric Walker and Oystein Fischer

Proceedings – Spectroscopic Studies of Superconductors (1996)

We present images of the flux line lattice and spectroscopic measurements of the vortex core region on the as grown (001) surface of an YBa2Cu3O7-(delta ) single crystal at 4.2 Kelvin. These measurements were done in a magnetic field of 6 Tesla applied parallel to the c-axis using scanning…

Ivan Maggio-Aprile, Christoph Renner, Andréas Erb, Eric Walker and Oystein Fischer

Journal of Low Temperature Physics 105 5-6, 1129-1134 (1996)

Scanning Tunneling Spectroscopy (STS) measurements have been carried out on the high Tc superconductor (HTS) YBa2Cu3O7−δ (YBCO). Using very high quality single crystals as well as hard tips, we obtained differential conductance spectra which showed various conductance features in agreement with…

Christoph Renner, Bernard Revaz, Jean-Yves Genoud and Oystein Fischer

Journal of Low Temperature Physics 105 5-6, 1083-1089 (1996)

We present local probe tunneling spectroscopy of Bi2Sr2CaCu2O8+delta single crystals for different oxygen concentrations, from optimally doped (T-c = 92.2 K) to highly overdoped (T-c = 56.0 K) phases. With increasing oxygen overdoping, the superconducting gap (Delta(p)) is reduced and the dip…

Ivan Maggio-Aprile, Christoph Renner, Andréas Erb, Eric Walker and Oystein Fischer

Physical Review Letters 75 14, 2754-2757 (1995)

We report the observation of the flux line lattice in YBa2Cu3O7−δ by scanning tunneling microscopy. The measurements were carried out at 4.2 K and in a magnetic field of 6 T applied along the c axis. The vortices appear arranged in an oblique lattice in which the primitive vectors are nearly…

Christoph Renner and Oystein Fischer

Physical Review. B, Condensed Matter 51 14, 9208-9218 (1995)

This paper reports very detailed low-temperature vacuum tunneling spectroscopy investigations of Bi2Sr2CaCu2O8+δ (BSCCO) single crystals. For clean vacuum junctions formed between a cleaved BSCCO single crystal and the normal-metal tip of a scanning tunneling microscope, we obtain stable c-axis…

Christoph Renner and Oystein Fischer

Physica C: Superconductivity and Its Applications 235-240, 53-56 (1994)

We present vacuum tunneling characteristics obtained on Bi2Sr2CaCu2O8+δ single crystals using a low temperature scanning tunneling microscope. We demonstrate very reproducible tunneling spectroscopy where the IV characteristics do not depend on modifications of the tunneling barrier obtained…

Christoph Renner and Oystein Fischer

Advances in superconductivity VI: proceedings of the 6th International Symposium on Superconductivity (ISS ’93), 429-434 (1994)

This paper reviews results obtained from low temperature scanning tunneling spectroscopy investigations on cleaved 2H-Nb1-xTaxSe2 and Bi2Sr2CaCu208 single crystals. Our study of the former crystals allowed us to image the vortex lattice, and to study how the peak in the density of states in the…

Christoph Renner and Oystein Fischer

Oxide superconductor physics and nano-engineering, 135-140 (1994)

We report STM spectroscopy measurements of in-situ cleaved Bi₂Sr₂CaCu₂O₈ single crystals at 4.8 Kelvin, where we achieved strong evidences for true vacuum tunneling. These careful experiments result in very reproducible spectroscopy as a function of position on the surface, and as a…

Christoph Renner, Oystein Fischer, Andrew Kent, D.B. Mitzi and A. Kapitulnik

Physica B: Condensed Matter 194-196, 1689-1690 (1994)

We report scanning tunneling spectroscopy investigations on in-situ cleaved superconducting Bi₂Sr₂CaCu₂O₈ single crystals. Although many investigators report reproducible tunneling studies on high temperature superconductors, there nevertheless remains uncertainties about the correct…

Bernardo Gaetano Barbiellini-Amidei, Oystein Fischer, Martin Peter, Christoph Renner and M. Weger

Physica C: Superconductivity and Its Applications 220 1-2, 55-60 (1994)

We discuss the conductance data of superconducting single crystal Bi2Sr2CaCu2Ox obtained with a scanning tunneling microscope in the vacuum tunneling mode. For this purpose, we introduce and apply a method involving filtering techniques to study the structure of the order parameter. We find that…

Ivan Maggio-Aprile, A.D. Kent, Philipp Niedermann, Christoph Renner, Louis Antognazza, Laurent Mieville, Olivier Brunner, Jean-Marc Triscone and Oystein Fischer

Ultramicroscopy 42-44, 728-733 (1992)

The surface structure of magnetron-sputtered YBa₂Cu₃O₇ thin films has been investigated using an STM operated in air. Both c-axis and a-axis oriented films have been investigated. In the case of c-axis thin films, different types of step and plateau structures are observed depending on the…

A.D. Kent, Christoph Renner, Philipp Niedermann, Jean-Gabriel Bosch and Oystein Fischer

Ultramicroscopy 42-44, 1632-1637 (1992)

We present the design of a scanning tunneling microscope (STM) that is operated in an ultra-high vacuum (UHV) chamber at room temperature and can be lowered into a standard helium crystat and cooled with helium exchange gas to low temperatures. Central to the design of our system is a compact…

Christoph Renner, Andrew Kent, Philipp Niedermann, Oystein Fischer and F. Lévy

Ultramicroscopy 42-44, 699-704 (1992)

Using a low-temperature scanning tunneling microscope, we have investigated the Abrikosov vortex lattice and its electronic structure on 2H-Nb₁₋ₓTaₓSe₂ single crystals for a range of Ta substitutions from x=0.00 to x=0.20 and with the magnetic field perpendicular to the basal plane. The…

Christoph Renner, Andrew Kent, Philipp Niedermann, Oystein Fischer and F. Lévy

Physical Review Letters 67 12, 1650-1652 (1991)

The local density of states of a superconducting vortex core has been measured as a function of disorder in the alloy system Nb1-xTaxSe2 using a low-temperature scanning tunneling microscope. The peak observed in the zero-bias conductance at a vortex center is found to be very sensitive to…

Andrew Kent, Jean-Marc Triscone, Louis Antognazza, Olivier Brunner, Christoph Renner, Philipp Niedermann, Michael Karkut and Oystein Fischer

Physica B: Condensed Matter 165-166, 1503-1504 (1990)

We report the superconducting properties of homogeneous highly oriented alloy thin films of Y1−xPrxBa2Cu3O7 prepared by a novel layer by layer method using do magnetron sputtering. As in the case of bulk material, we find a continuous suppression of the superconducting transition temperature with …

Christoph Renner, Philipp Niedermann, A. D. Kent and Oystein Fischer

Review of Scientific Instruments 61 3, 965-967 (1990)

We have developed a linear translation device using piezoelectric‐induced slip‐stick motion. Reproducible single steps of about 30 Å, as well as continuous stepping with an overall translation speed of 0.25 mm/s, are routinely realized. The notable feature of this device is that this…

Christoph Renner, Philipp Niedermann, Andrew Kent and Oystein Fischer

Journal of Vacuum Science & Technology. A: Vacuum, Surfaces, and Films 8 1, 330-332 (1990)

We present a new scanning tunneling microscope (STM) developed specifically for use at low temperatures within a standard helium cryostat. This compact STM (diameter 25 mm and length 61 mm) has been designed to be compatible with a superconducting magnet. It incorporates a novel approach system…

Philipp Niedermann, Christoph Renner, Andrew Kent and Oystein Fischer

Journal of Vacuum Science & Technology. A: Vacuum, Surfaces, and Films 8 1, 594-597 (1990)

Field emission from broad metal cathodes is known to be strongly enhanced at a small number of emitting sites per cm2 compared to the expected Fowler–Nordheim emission from ideal, flat surfaces. We have operated a scanning tunneling microscope (STM) in the field emission regime (typical tip…

Andrew Kent, Ivan Maggio-Aprile, Philipp Niedermann, Christoph Renner, Jean-Marc Triscone, Michael Karkut, Olivier Brunner, Louis Antognazza and Oystein Fischer

Physica C: Superconductivity and Its Applications 162-164, 1035-1036 (1989)

We have made measurements of the local potential distribution and topography of current carrying Y1Ba2Cu3O6.9 thin films using a scanning tunneling microscope. We have compared the electrostatic potential distribution in the normal state on post-annealed thin films and in-situ prepared films. On…

Christoph Renner, Philipp Niedermann and Oystein Fischer

IEEE Transactions on Electrical Insulation 24 6, 911-916 (1989)

Enhanced field emission on high-purity aluminum has been investigated. The current/voltage characteristic (Fowler-Nordheim plot), the chemical composition as determined by Auger electron spectroscopy and X-ray microprobe analysis, and the topography of field-emitting sites were studied locally. In…

Philipp Niedermann, Christoph Renner, Andrew Kent and Oystein Fischer

Proceedings of the International Conference on Vacuum Microelectronics (2nd), 173-176 (1989)

A study of enhanced field emission on broad area niobium cathodes is presented. Emitting sites have been investigated by field emission scans, scanning electron microscopy and scanning tunneling microscopy. All except one of 14 studied emitters are of micron or submicron size. A trend is observed…

Tejas Parasram Singar

Thèse, 169 (2024)

High-temperature superconductors have been extensively studied over the past four decades. Much progress has been made in terms of understanding the basic fundamental mechanisms that lead to exceptionally high transition temperatures as compared to conventional superconductors. However, many…

Vincent Pasquier

Thèse (2023)

Strain, which results from the deformation of a material, is used as a tuning parameter to study the charge density wave (CDW) phase in transition metal dichalcogenides (TMDs). We have developed two bending devices to apply uniaxial or biaxial strain to low-dimensional materials. Characterization…

Tim Gazdic

Thèse (2020)

We study high temperature superconductivity of heavily overdoped (p~0.22) Bi2Sr2CaCu2O8+d with the objective to find signatures of the more conventional superconductivity anticipated in comparison to its more widely studied underdoped counterpart. We find some similarities as well as distinctly…

Marcello Spera

Thèse (2019)

In this work, we performed a detailed scanning tunnelling microscopy and spectroscopy study of the charge density wave state of 1T-CuxTiSe2 in a wide range of Cu concentrations (0 < x < 0.07), an apparently perfect playground for investigating the interplay between correlated ground states. Thanks...

Arpad Pasztor

Thèse (2018)

The charge density wave (CDW) phase in bulk and exfoliated crystals of transition metal dichalcogenides was studied by scanning tunneling microscopy (STM). In exfoliated flakes of VSe2 we found a striking non-monotonic evolution of the CDW transition temperature as function of thickness derived…

Renan Villarreal

Thèse (2017)

Manganese self-assembles into atomic chains on the Si(001) reconstructed surface. Our combined scanning tunneling microscopy, atomic force microscopy (AFM) and density functional theory (DFT) study revealed a simple necklace-like structure of the Mn chains. The DFT calculated adsorption energies…

Thomas Amundsen

Thèse (2016)

We present a scanning tunnelling microscopy study of the metal insulator (MI) phase transition in NdNiO3 thin films grown on NdGaO3. Although topographic resolution is limited to grain structures and step edges, we did achieve high resolution and reproducible spectroscopic mapping of the thin film…

Anna Maria Novello

Thèse (2015)

The interplay between charge order and superconductivity has been a long standing puzzle in a wide range of superconducting materials. The transition metal dichalcogenide 1T-TiSe2 is an interesting material that can give an important contribution to this debate. Indeed, 1T-TiSe2 undergoes a charge…

Jens Erik Bruer

Thèse (2014)

The mechanism underlying high temperature superconductivity continues to challenge our understanding. Scanning tunneling spectroscopy (STM) has historically been one of the prime techniques to tackle superconductivity in conventional BCS materials, providing key insight into the pairing mechanism….

François Bianco

Thèse (2013)

Dans ce travail, nous nous sommes intéressé à l’auto assemblage de nanolignes de bismuth sur la surface du silicium et des structures dérivées de ces nanolignes. Nous avons découvert que l’hydrogénation permet d’enlever complètement le bismuth de la surface tout en conservant la…