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Project Summary: FeTe0.55Se0.45 (FTS) occupies a special spot in modern condensed matter physics at the intersections of electron correlation, topology, and unconventional superconductivity. The bulk electronic structure of FTS is predicted to be topologically nontrivial due to the band inversion between the dxz and pz bands. However, there remain debates in both the authenticity of the Dirac surface states (DSSs) and the experimental deviations of band structure from the theoretical picture. The Shen group at Stanford recently resolved these debates through a comprehensive angle-resolved photoemission spectroscopy (ARPES) investigation. They first observe a persistent DSS independent of kz. Then, by comparing FTS with FeSe, they identify the fingerprint of the inversion between the dxz and pz bands. Their results highlight the significant influence of correlation on modifying the band structure and make a strong case for the existence of topological band structure in this unconventional superconductor.
Publication: Y.F. Li et al., Phys. Rev. X 14, 021043 (2024).
DOI: 10.1103/PhysRevX.14.021043
2DCC Role:The FTS sample quality is critical for this experiment. While it is challenging to produce high-quality FTS samples with high superconducting volume fraction, the 2DCCâs bulk synthesis team successfully synthesized FTS samples with nearly ideal quality, which made this impactful work possible.