Article, 2024

Lateral Quantum Confinement Effect on High‑TC Superconducting FeSe Monolayer

Nano Letters, ISSN 1530-6984, 1530-6992, Volume 24, 25, Pages 7654-7661, 10.1021/acs.nanolett.4c01435

Contributors

He, Guanyang [1] [2] Li, Yu [2] Lei, Yuxuan [2] [3] Kreisel, Andreas [4] Andersen, Brian Møller 0000-0002-9786-7553 [4] Wang, Jian 0000-0002-7945-0826 (Corresponding author) [2] [5] [6]

Affiliations

  1. [1] ShanghaiTech University
    2. [NORA names: China; Asia, East];
  2. [2] Peking University
    3. [NORA names: China; Asia, East];
  3. [3] Beijing Academy of Quantum Information Sciences
    4. [NORA names: China; Asia, East];
  4. [4] University of Copenhagen
    5. [NORA names: KU University of Copenhagen; University; Denmark; Europe, EU; Nordic; OECD];
  5. [5] Collaborative Innovation Center of Quantum Matter
    6. [NORA names: China; Asia, East];

Abstract

Despite decades of research in spatially confined superconducting systems to understand the modification of superconductivity from reduced length scales, the investigation of the quantum confinement effect on high-temperature superconductors remains an outstanding challenge. Here, we report scanning tunneling spectroscopy measurements on laterally confined FeSe monolayers on SrTiO3 substrates, which are formed by epitaxially growing FeSe films with a coverage less than one unit cell. Comparing to the uniform regions of FeSe monolayers, the peninsula regions at the monolayer boundary exhibit reduced Fermi energy and undiminished superconductivity, leading to a putative crossover from a Bardeen-Cooper-Schrieffer state to a Bose-Einstein condensate state. In isolated FeSe monolayer islands, superconductivity is shown to exist in samples of smaller volume in contrast to conventional superconductors, while the validity of Anderson's criterion remains fulfilled. Our work reveals lateral quantum confinement effects in unconventional superconductors to enrich the understanding of high-temperature superconductivity in low-dimensional systems.

Keywords

Anderson criteria, Bardeen-Cooper-Schrieffer state, Bose-Einstein condensate state, FeSe, FeSe films, FeSe monolayer, Fermi energy, Peninsula, Peninsula region, SrTiO, boundaries, cells, condensed state, confinement effect, conventional superconductors, criteria, crossover, decades, decades of research, effect, energy, films, high-Tc, high-temperature superconductivity, high-temperature superconductors, investigation, islands, lateral quantum confinement effect, lateralization, length scales, low-dimensional systems, measurements, modification, monolayer, monolayer boundary, monolayer islands, quantum confinement effect, reduced Fermi energy, reduced length scales, region, research, samples, samples of small volume, scale, scanning tunneling spectroscopy measurements, small volume, spectroscopy measurements, state, substrate, superconducting systems, superconductivity, superconductors, system, unconventional superconductors, uniform regions, unit cell, units, validity, volume

Funders

  • National Natural Science Foundation of China
  • Ministry of Science and Technology of the People's Republic of China

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