Pressure-induced dimensional crossover in a kagome superconductor

TL;DR

This study investigates how high pressure induces a dimensional crossover in a kagome superconductor, leading to a new superconducting phase linked to structural and electronic changes, including a topological transition.

Contribution

It reveals the origin of the high-pressure superconducting phase in CsV3Sb5 as driven by interlayer Sb2-Sb2 bonding and dimensional crossover, supported by experiments and first-principles calculations.

Findings

New superconducting phase emerges under moderate pressure.

Dimensional crossover from 2D to 3D enhances Tc.

High pressure induces a topological phase transition.

Abstract

The recently discovered kagome superconductors AV3Sb5 exhibit tantalizing high-pressure phase diagrams, in which a new dome-like superconducting phase emerges under moderate pressure. However, its origin is as yet unknown. Here, we carried out the high-pressure electrical measurements up to 150 GPa, together with the high-pressure X-ray diffraction measurements and first-principles calculations on CsV3Sb5. We find the new superconducting phase to be rather robust and inherently linked to the interlayer Sb2-Sb2 interactions. The formation of Sb2-Sb2 bonds at high pressure tunes the system from two-dimensional to three-dimensional and pushes the Pz orbital of Sb2 upward across the Fermi level, resulting in enhanced density of states and increase of TC. Our work demonstrates that the dimensional crossover at high pressure can induce a topological phase transition and is related to the abnormal high-pressure TC evolution. Our findings should apply for other layered materials.