Quantum vortex core and missing pseudogap in the multi-band BCS-BEC-crossover superconductor FeSe

Abstract

FeSe is argued as a superconductor in the Bardeen-Cooper-Schrieffer Bose-Einstein-condensation crossover regime where the superconducting-gap size and the superconducting transition temperature Tc are comparable to the Fermi energy. In this regime, vortex bound states should be well quantized and the preformed pairs above Tc may yield a pseudogap in the quasiparticle-excitation spectrum. We performed spectroscopic-imaging scanning tunneling microscopy to search for these features. We found Friedel-like oscillations near the vortex, which manifest the quantized levels, whereas the pseudogap was not detected. These apparently conflicting observations may be related to the multi-band nature of FeSe.

5 pages, 4 figures. To appear in PRL. Supplemental Material is available at http://www.riken.jp/epmrt/Hanaguri/SI/FeSe_Vortex_Tdep_SM.pdf

References in corpus (7)

• Field-induced superconducting phase of FeSe in the BCS-BEC cross-over
• Emergence of the nematic electronic state in FeSe
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Nematicity, magnetism and superconductivity in FeSe
• Anomalous Fermi surface in FeSe seen by Shubnikov-de Haas oscillation measurements
• Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover
• Pseudogap Behavior of the Nuclear Spin-lattice Relaxation Rate in FeSe Probed by ${}^{77}$Se-NMR

Cited by in corpus (1)

• Enhanced critical temperature, pairing fluctuation effects, and BCS-BEC crossover in a two-band Fermi gas