Anomalous metallic state in the vicinity of Metal to Valence Bond Solid insulator transition in LiVS2

TL;DR

This paper studies LiVS2 and LiVSe2, revealing an anomalous metallic state near the metal-insulator transition in LiVS2, with evidence of valence bond solid fluctuations and the role of itinerancy in VBS formation.

Contribution

It introduces LiVS2 as a new system exhibiting a VBS transition near metallicity and suggests itinerant electrons influence VBS formation.

Findings

LiVS2 transitions from a paramagnetic metal to a VBS insulator at 305 K.

LiVS2's high-temperature phase exhibits a pseudo-gap likely due to VBS fluctuations.

LiVSe2 remains a paramagnetic metal down to 2 K.

Abstract

We investigate LiVS2 and LiVSe2 with a triangular lattice as itinerant analogues of LiVO2, known for the formation of valence bond solid (VBS) state out of S = 1 frustrated magnet. LiVS2, which is located at the border between a metal and a correlated insulator, shows a first ordered transition from a paramagnetic metal to a VBS insulator at Tc ~ 305 K upon cooling. The presence of VBS state in the close vicinity of insulator-metal transition may suggest the importance of itinerancy in the formation of VBS state. We argue that the high temperature metallic phase of LiVS2 has a pseudo-gap, likely originating from the VBS fluctuation. LiVSe2 was found to be a paramagnetic metal down to 2 K.