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

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.