Spectroscopic evidence for negative electronic compressibility in a quasi-three-dimensional spin-orbit correlated metal

TL;DR

This study provides spectroscopic evidence of negative electronic compressibility in a 3D correlated metal, revealing a new pathway for exploring NEC in bulk materials with potential nanoelectronic applications.

Contribution

It demonstrates for the first time negative electronic compressibility in a quasi-3D spin-orbit correlated metal using ARPES, expanding the understanding of NEC beyond low-dimensional systems.

Findings

Observation of anomalous decrease in chemical potential with increased electron filling

Lowering of conduction band energy linked to reduced bandgap and NEC

Potential for NEC in bulk correlated metals for nanoelectronics applications

Abstract

Negative compressibility is a sign of thermodynamic instability of open or non-equilibrium systems. In quantum materials consisting of multiple mutually coupled subsystems, the compressibility of one subsystem can be negative if it is countered by positive compressibility of the others. Manifestations of this effect have so far been limited to low-dimensional dilute electron systems. Here we present evidence from angle-resolved photoemission spectroscopy (ARPES) for negative electronic compressibility (NEC) in the quasi-three-dimensional (3D) spin-orbit correlated metal (Sr1-xLax)3Ir2O7. Increased electron filling accompanies an anomalous decrease of the chemical potential, as indicated by the overall movement of the deep valence bands. Such anomaly, suggestive of NEC, is shown to be primarily driven by the lowering in energy of the conduction band as the correlated bandgap reduces. Our finding points to a distinct pathway towards an uncharted territory of NEC featuring bulk correlated metals with unique potential for applications in low-power nanoelectronics and novel metamaterials.