Orbital-selective two-gap superconductivity in kagome metal CsV3Sb5

TL;DR

This paper theoretically investigates the orbital-dependent multi-gap superconductivity in kagome metal CsV3Sb5, revealing how different orbitals contribute to distinct superconducting gaps and their coupling to phonon modes.

Contribution

It demonstrates that orbital-selective pairing explains the observed two-gap superconductivity in CsV3Sb5, highlighting the role of specific orbitals and phonon interactions.

Findings

Two distinct superconducting gaps with different orbital origins.

Strong coupling of V-3d orbitals to specific phonon modes.

Weak coupling of Sb-5pz orbitals to out-of-plane vibrations.

Abstract

Recent experiments have revealed anisotropic multi-gap superconductivity in the kagome metal CsV3Sb5. However, the impact of multi-orbital character and electron-phonon coupling (EPC) on the multiple superconducting gaps remains not fully understood. In this work, we theoretically investigate the multi-orbital electronic structure and superconducting gap properties of CsV3Sb5 by combining first-principles calculations with superconducting density functional theory (SCDFT). Our results demonstrate that orbital-selective pairing drives the observed two-gap superconductivity in CsV3Sb5. Specifically, the two distinct gaps exhibit strong orbital dependence: a large, highly anisotropic gap (average magnitude ~0.64 meV) primarily originates from V-3d orbitals, while a small, isotropic gap (~0.25 meV) is associated with the Sb-5pz orbital. The V-3d orbitals exhibit strong coupling to the in-plane V-V bond-stretching and out-of-plane V-Sb bending phonon modes, whereas the Sb-5pz orbitals show weak coupling to the out-of-plane vibrations of both Cs and the apical Sb atoms. These findings provide fundamental insights into the orbital-selective superconductivity and EPC mechanisms in kagome CsV3Sb5.