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Signatures of Amorphous Shiba State in FeTe0.55Se0.45

Year: 2025
Type: article
Abstract: is a peculiar material: it hosts surface states with a Dirac dispersion, is a putative topological superconductor hosting Majorana modes in vortices, and has an unusually low Fermi energy. The superconducting state is generally characterized by three gaps in different bands, with the homogeneous, spatially extended Bogoliubov excitations─in this work, we uncover evidence that it is instead of a very different nature. Our scanning tunneling spectroscopy data show several peaks in the density of states above a full gap, and by analyzing their spatial and junction-resistance dependence, we conclude the peaks above the first one are not coherence peaks from different bands. Instead, comparisons with our simulations indicate they originate from generalized Shiba states that are spatially overlapping. This can lead to an amorphous state of Bogoliubov quasiparticles, reminiscent of impurity bands in semiconductors. We discuss the origin and implications of this new state.
Source: Nano Letters
DOI: 10.1021/acs.nanolett.4c05650
Authors: Jinwon Lee, Sanghun Lee, Andreas Kreisel, Jens Paaske, Brian M. Andersen, Koen M. Bastiaans, Damianos Chatzopoulos, Genda Gu, Doohee Cho, Milan P. Allan
Institutions: Leiden University, Yonsei University, University of Copenhagen, Brookhaven National Laboratory, Center for NanoScience, Munich Center for Quantum Science and Technology, Ludwig-Maximilians-Universität München
Language: English
Open Access status: hybrid
Estimated APC paid: $4,500
Funders: U.S. Department of Energy, National Research Foundation, Universiteit Leiden, Technische Universiteit Delft, Yonsei University, National Research Foundation of Korea, Brookhaven National Laboratory, H2020 European Research Council
Awards: G1049420640, G1285306620, G2191254144, G241279073, G3262563802, G5765906131, G5835071566, G88078941
OpenAlex ID: W4407423386
FWCI: 0.737
Cites: 52
Cited by: 2
Related to: 10