Observation of anomalous temperature dependence of spectrum on small Fermi surfaces in a BiS2-based superconductor

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal unusual temperature-dependent spectral features in a BiS2-based superconductor, indicating strong electronic interactions involved in superconductivity.

Contribution

It provides the first detailed observation of temperature-dependent spectral anomalies on small Fermi surfaces in a BiS2 superconductor.

Findings

Small electron-like Fermi surfaces observed around X point.

A broad hump in the spectrum is suppressed with increasing temperature.

Dispersive band features remain unaffected by temperature.

Abstract

We performed an angle-resolved photoemission spectroscopy study of the BiS2-based superconductor Nd(O,F)BiS2. Two small electron-like Fermi surfaces around X (pi, 0) are observed, which enclose 2.4% and 1.1% of the Brillouin zone area, respectively, corresponding to an electron doping of 7% per Bi site. The low-energy spectrum consists of a weakly-dispersing broad hump and a dispersive branch, which follows well the calculated band dispersion. This hump is drastically suppressed with increasing temperature, while the dispersive branch is essentially unaffected. The anomalous thermal effect indicates a highly interacting electronic state, in which the superconducting pairing develops.