Isabel Guillamon

Superconducting Density of States and Vortex Cores of 2H-NbS2

Scanning tunneling microscopy and spectroscopy measurements in the superconducting dichalcogenide 2H-NbS2 show a peculiar superconducting density of states with two well-defined features at 0.97 and 0.53 meV, located, respectively, above and below the value for the superconducting gap expected from the single band s-wave BCS model (Delta=1.76k_(B)T_(c)=0.9 meV). Both features have a continuous temperature evolution and disappear at T_(c)=5.7 K. Moreover, we observe the hexagonal vortex lattice with radially symmetric vortices and a well-developed localized state at the vortex cores. The sixfold star shape characteristic of the vortex lattice of the compound 2H-NbSe2 is, together with the charge density wave order, absent in 2H-NbS2.

Direct observation of melting in a two-dimensional superconducting vortex lattice

A two-dimensional lattice of vortices melts into an isotropic liquid with increasing temperature. A microscopic view of the melting transition reveals that this actually occurs in three steps, one of which is an unusual liquid-crystal-like vortex phase.

Nanoscale superconducting properties of amorphous W-based deposits grown with a focused-ion-beam

We present very low temperature scanning tunneling microscopy and spectroscopy (STM/S) measurements in W-based amorphous superconducting nanodeposits grown using a metal–organic precursor and a focused-ion-beam. The superconducting gap closely follows s-wave Bardeen–Cooper– Schrieffer theory, and STS images under magnetic fields show a hexagonal vortex lattice whose orientation is related to features observed in the topography through STM. Our results demonstrate that the superconducting properties at the surface of these deposits are very homogeneous, down to atomic scale.

Intrinsic atomic-scale modulations of the superconducting gap of 2 H − NbSe 2

We present scanning tunneling microscopy and spectroscopy measurements at 100 mK in the superconducting material

A nodeless superconducting gap in Sr 2 RuO 4 from tunneling spectroscopy

2H\text{\ensuremath{-}}{\text{NbSe}}_{2}

Magnetic field dependence of the density of states in the multiband superconductor β-Bi2Pd

that show well defined features in the superconducting density of states, with changes that follow atomic periodicity. Our experiment demonstrates that the intrinsic superconducting density of states can show atomic size modulations, which reflect the reciprocal space structure of the superconducting gap. In particular, we obtain that the superconducting gap of

Transport properties of superconducting amorphous W-based nanowires fabricated by focused-ion-beam-induced-deposition for applications in Nanotechnology

2H\text{\ensuremath{-}}{\text{NbSe}}_{2}

Field dependence of the vortex core size probed by scanning tunneling microscopy

has sixfold modulated components at 0.75 and 1.2 mV. Moreover, we also find related atomic size modulations inside vortices, demonstrating that the much discussed star shape vortex structure produced by localized states inside the vortex cores has a superposed atomic size modulation, which has hitherto been undetected. The tip substrate interaction in an anisotropic superconductor has been calculated, giving position dependent changes related to the observed gap anisotropy.

Three axis vector magnet set-up for cryogenic scanning probe microscopy

We report on tunneling spectroscopy measurements using a scanning tunneling microscope (STM) on the spin triplet superconductor Sr2RuO4. A fully open gap, close to the Bardeen-Cooper-Schrieffer (BCS) value, is found, which disappears at the bulk Tc = 1.5K. The results are discussed in the framework of recent multigap scenarios for an unconventional spin triplet superconductor.H. Suderow, V. Crespo, I. Guillamon, S. Vieira, F. Servant, P. Lejay, J.P. Brison, and J. Flouquet Laboratorio de Bajas Temperaturas, Departamento de F́ısica de la Materia Condensada Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias Universidad Autónoma de Madrid, 28049 Madrid, Spain Institut Néel, CNRS / UJF, 25, Av. des Martyrs, BP166, 38042 Grenoble Cedex 9, France CEA, INAC, SPSMS, 38054 Grenoble, France (Dated: November 12, 2008)

Scanning tunneling measurements of layers of superconducting 2H-TaSe2: Evidence for a zero-bias anomaly in single layers

We present very low-temperature scanning tunneling microscopy (STM) experiments on single-crystalline samples of the superconductor