Pressure Tuning of Electronic Correlations and Flat Bands in CsCr$_3$Sb$_5$

TL;DR

This study investigates how applying pressure affects the electronic properties and phases of CsCr$_3$Sb$_5$, revealing that pressure weakens electronic correlations and suppresses ordered states, leading to superconductivity.

Contribution

The paper provides a systematic DFT+DMFT analysis of pressure effects on CsCr$_3$Sb$_5$, highlighting the interplay between flat bands, correlations, and phase transitions.

Findings

Pressure suppresses charge- and spin-density-wave order.

Electronic correlations weaken under pressure due to orbital hybridization.

Superconductivity emerges as ordered phases are suppressed.

Abstract

CsCr$_3$Sb$_5$ is a newly identified strongly correlated kagome superconductor, characterized by non-Fermi-liquid behavior at elevated temperatures and intertwined charge- and spin-density-wave order below $T_{DW}\approx 54$K. Under external pressure, this order is suppressed and a superconducting phase emerges. This phase diagram, which closely resembles that of high-$T_c$ superconductors, together with a kagome flat band near the Fermi level and possible altermagnetic order, has motivated extensive theoretical and experimental investigations. To better understand how pressure influences the ordered states, we present a systematic study of the evolution of the electronic properties under applied pressure. Performing DFT+DMFT (density functional theory combined with dynamical mean field theory) calculations, we uncover a complex interplay between the redistribution of spectral weight in the flat bands and the strength of electronic correlations under pressure. Our results further strengthen the interpretation that pressure effectively weakens electronic correlations through enhanced orbital hybridization. This, in turn, strongly suggests that superconductivity emerges as a direct consequence of the suppression of the system's ordered phase.