Year: 2023
Type: article
Abstract: The quantum many-body states in the Bardeen-Cooper-Schrieffer--Bose-Einstein condensation (BCS-BEC) crossover regime are of long-lasting interest. Here we report direct spectroscopic evidence of BCS-BEC crossover in real space in a FeSe monolayer thin film by using spatially resolved scanning tunneling spectra. The crossover is driven by the shift of band structure relative to the Fermi level. The theoretical calculation based on a two-band model qualitatively reproduces the measured spectra in the whole crossover range. In addition, the Zeeman splitting of the quasiparticle states is found to be consistent with the characteristics of a condensate. Our work paves the way to study the exotic states of BCS-BEC crossover in a two-dimensional crystalline material at the atomic scale.
Institutions: State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, University of Southern California, Universität Hamburg, Collaborative Innovation Center of Quantum Matter, Frontier Science Center for Quantum Information of the Ministry of Education of China, Constructor University, Pohang University of Science and Technology
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4361217172