Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 100: Electronic Structure of Surfaces II
O 100.3: Talk
Thursday, March 19, 2020, 11:00–11:15, REC C 213
Observation of anisotropic vortices on clean superconducting Nb(110) — •Felix Friedrich, Artem B. Odobesko, Robin Boshuis, Stefan Wilfert, and Matthias Bode — Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
The quest for Majorana zero modes in solid state systems requires the possibility to distinguish between
true zero energy modes and the variety of other, trivial, modes that can occur inside the superconducting gap.
Large values of the gap facilitate the analysis of these in-gap states.
We suggest the clean Nb(110) surface that we obtain by electron beam heating [1]
as a suitable platform for future investigations of possible topological states
due to its large superconducting gap ΔNb ≈ 1.53 meV.
We use low-temperature STM/STS to examine the response of the Nb(110) surface to an external magnetic field.
As a type-II superconductor, Nb(110) develops an Abrikosov lattice of vortices.
Spectroscopy measurements at the vortex core reveal conductance peaks around zero bias,
which we attribute to Caroli-de Gennes-Matricon states.
Intriguingly, dI/dU maps recorded at bias voltages corresponding to energies
inside the superconducting gap uncover an anisotropic shape of the vortices.
We explain this observation with the pronounced nesting of the Fermi surface of Nb(110).
[1] A. B. Odobesko et al., Phys. Rev. B 99, 115437 (2019).