Evolution of Band Structure in a Kagome Superconductor Cs(V1-xCrx)3Sb5: Toward Universal Understanding of CDW and Superconducting Phase Diagrams

TL;DR

This study investigates how Cr substitution affects the electronic structure and phase diagram of Cs(V1-xCrx)3Sb5, revealing orbital-selective band shifts and the disappearance of CDW, advancing understanding of superconductivity and CDW interplay.

Contribution

It provides a systematic ARPES analysis of Cr-doped CsV3Sb5, highlighting orbital-specific band shifts and the conditions for CDW suppression, offering insights into the electronic origins of phase transitions.

Findings

Cr doping causes energy shifts in V-derived bands but not Sb bands.

The three-dimensional CDW vanishes at x=0.25, correlating with band changes.

Proximity of saddle points to the Fermi level is crucial for phase behavior.

Abstract

Kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit a characteristic superconducting and charge-density wave (CDW) phase diagram upon carrier doping and chemical substitution. However, the key electronic states responsible for such a phase diagram have yet to be clarified. Here we report a systematic micro-focused angle-resolved photoemission spectroscopy (ARPES) study of Cs(V1-xCrx)3Sb5 as a function of Cr content x, where Cr substitution causes monotonic reduction of superconducting and CDW transition temperatures. We found that the V-derived bands forming saddle points at the M point and Dirac nodes along high-symmetry cuts show an energy shift due to electron doping by Cr substitution, whereas the Sb-derived electron band at the Gamma point remains almost unchanged, signifying an orbital-selective band shift. We also found that band doubling associated with the emergence of three-dimensional CDW identified at x = 0 vanishes at x = 0.25, in line with the disappearance of CDW. A comparison of band diagrams among Ti-, Nb-, and Cr-substituted Cs(V1-xCrx)3Sb5 suggests the importance to simultaneously take into account the two saddle points at the M point and their proximity to the Fermi energy, to understand the complex phase diagram against carrier doping and chemical pressure.