Compression-induced magnetic obstructed atomic insulator and spin singlet state in antiferromagnetic KV2Se2O

TL;DR

This study reveals a pressure-induced insulator in KV2Se2O, driven by magnetic and electronic changes without structural phase transition, providing new insights into metal-insulator transitions in complex materials.

Contribution

It demonstrates a novel pressure-driven metal-insulator transition in KV2Se2O that occurs without structural change, identifying a magnetic obstructed atomic insulator with a spin-singlet state.

Findings

Insulating gap of 40 meV at 43.5 GPa

Carrier type switching indicating Fermi surface reconstruction

Identification of a magnetic obstructed atomic insulator with spin-singlet state

Abstract

Among the complex many-body systems, the metal-insulator transition stands out as a cornerstone and a particularly fertile ground for scientific inquiry. The established models including Mott insulator, Anderson localization and Peierls transition, are still insufficient to capture the complex and intertwined phenomena observed in certain material systems. KV2Se2O, a newly discovered room-temperature altermagnetic candidate exhibiting a spin-density-wave transition below 100 K, provides a unique platform to investigate the interplay of many-body effects and unconventional magnetism, specifically the anticipated metal-insulator transition under extreme conditions. Here, we report a compression-induced insulator by suppressing the metallic behavior without structural phase transition. The newly opened gap is estimated to be 40 meV at around 43.5 GPa, given direct evidence for the insulating state. A concurrent switching of carrier type demonstrates the large Fermi surface reconstruction crossing the metal-insulator transition. The density functional theory calculations indicate that the discovered V+2.5-based insulator is a magnetic obstructed atomic insulator, being a spin-singlet state with bonding orbital order. This work not only presents an archetype of a pressure-driven metal-insulator transition decoupled from structural change but also delivers fundamental physical insights into the metal-insulator transition.