arXiv subjects

C. Chapelier

Publications and source records attributed to C. Chapelier.

21 records · Page 2Linked to original sources

arXiv2005

Ballistic effects in a proximity induced superconducting diffusive metal

Using a Scanning Tunneling Microscope (STM), we investigate the Local Density of States (LDOS) of artificially fabricated normal metal nano-structures in contact with a superconductor. Very low temperature local spectroscopic measurements (100 mK) reveal the presence of well defined subgap peaks at energy |E|<Delta in the LDOS at various positions of the STM tip. Although no clear correlations between the LDOS and the shape of the samples have emerged, some of the peak features suggest they originate from quasi-particle bound states within the normal metal structures (De Gennes St James states). Refocusing of electronic trajectories induced by the granular srtucture of the samples can explain the observation of spatially uncorrelated interference effects in a non-ballistic medium.

cond-mat.mes-hall↗

arXiv2004

Anomalous proximity effect in an inhomogeneous disordered superconductor

By combining very low temperature scanning tunneling microscopy and spectroscopy on a TiN film we have observed a non uniform state comprising of superconducting (S) and normal (N) areas. The local density of states displays a spatial dependence between S and N different from the usual proximity effect. We conclude that mesoscopic fluctuations might play a major role in accordance with recent theories on superconductor-normal metal quantum transition.

cond-mat.supr-con↗

arXiv2000

Spatially resolved spectroscopy on a superconducting proximity structure

We investigated the local density of states (LDOS) of a normal metal (N) in good electrical contact with a superconductor (S) as a function of the distance $x$ to the NS interface. The sample consists of a pattern of alternate stripes of Au and Nb made by UV-lithography. We used a low temperature scanning tunneling microscope to record simultaneously $dI/dV(V,x)$ curves and the topographic profile $z(x)$. Nearby the NS interface, all the spectra show a dip near the Fermi energy but depending on the geometry, different behaviours can be distinguished. First, when the characteristic size of the normal metal $L$ is much larger than the coherence length $ξ_N \simeq \sqrt{\hbar D_N/ 2Δ}$, the spectral extension of the dip decreases from $Δ$ at the NS interface to zero at distances $x\ggξ_N$. Second, when $L$ is comparable to $ξ_N$ the apparent gap in the LDOS is space-independent and related to the Thouless energy.

cond-mat.mes-hall↗