Surface-termination-dependent electronic states in kagome superconductors AV3Sb5 (A = K, Rb, Cs) studied by micro-ARPES

TL;DR

This study uses micro-ARPES to reveal how surface termination affects electronic states and charge-density wave properties in kagome superconductors AV3Sb5, providing insights into their complex surface-dependent phenomena.

Contribution

It uncovers the surface-termination-dependent electronic structures and CDW behaviors in AV3Sb5 superconductors, highlighting the diversity of their ground states.

Findings

Distinct polar surfaces depend on termination type.

K-terminated surfaces show band splitting; Sb-terminated do not.

Different CDW structures are observed on different terminations.

Abstract

Recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit exotic bulk and surface physical properties such as charge-density wave (CDW) and chirality, whereas their origins remain unresolved. By using micro-focused angle-resolved photoemission spectroscopy, we discovered that AV3Sb5 commonly exhibits two distinct polar surfaces depending on the termination; electron- and hole-doped ones for the A- and Sb-termination, respectively. We observed that the kagome-derived band shows a clear splitting in the A-terminated surface while it is absent in the Sb-terminated counterpart, indicative of the polarity-dependent CDW at the surface. Close comparison of the band-dependent splitting reveals that the three-dimensional CDW structure of the K-terminated surface is different from that of the Rb- or Cs-terminated surface, suggesting the diversity of the CDW ground state. These results provide important insight into the origin of CDW in kagome superconductors AV3Sb5.