condensed matter physics

Coupled Spin-Density-Wave and Bond-Order Driven Metal-Insulator Transition in Altermagnetic CsCrSO

arXiv:2607.28329

summary

The paper identifies a metal‑insulator transition in CsCr₂S₂O that arises from a bond‑order instability coupled to a secondary spin‑density wave, enabled by pre‑existing altermagnetic C‑type antiferromagnetism and orbital‑selective electronic behavior.

Abstract

A metal-insulator transition (MIT) driven by bond order (BO) coupled with a secondary spin-density wave (SDW) is identified in CsCrSO. Such coupling is enabled as a result of the broken time-reversal symmetry due to the pre-existing C-type antiferromagnetic (C-AFM) order. First-principles calculations reveal an orbital-selective physics that Cr- orbitals form local moments and establish the altermagnetic order, while the Cr- orbitals remain metallic and hybridize with S-. Thus the low-energy physics is governed by the Cr- and S- orbitals. On-site interactions then enhance a secondary SDW (SDW) instability of the itinerant electrons, which couples to the Cr--S- bonding order. The resulting coupled SDW-BO simultaneously produces experimentally observed structural distortion, charge disproportionation, local Cr-moment modulation, and gap opening. Our results establish an orbital-selective mechanism upon which pre-existing altermagnetism and electronic correlations cooperate to drive a structural MIT.

Topics & keywords

#metal-insulator transition#altermagnetism#spin-density wave#bond order#orbital-selective physics#first-principles calculationsCsCr2S2OC-type antiferromagnetismCr d_{xz} orbitalCr d_{yz} orbitalS p_z hybridizationdensity functional theory