# Isostructural Mott Transition in 2D honeycomb antiferromagnet V$_{0.9}$PS$_3$

## TL;DR

This study reports an isostructural Mott insulator-metal transition in 2D honeycomb V$_{0.9}$PS$_3$ under high pressure, revealing a pressure-induced transition without lattice distortions, contrasting with other MPX$_3$ materials.

## Contribution

First observation of an isostructural Mott transition in a van-der-Waals 2D honeycomb antiferromagnet V$_{0.9}$PS$_3$, expanding understanding of pressure-induced electronic phase changes.

## Key findings

- Insulating resistivity follows variable-range hopping behavior.
- Transition to metallic resistivity occurs between 112 and 124 kbar.
- No structural change at the insulator-metal transition, indicating an isostructural transition.

## Abstract

We present the observation of an isostructural Mott insulator-metal transition in van-der-Waals honeycomb antiferromagnet V$_{0.9}$PS$_3$ through high-pressure x-ray diffraction and transport measurements. The MPX$_3$ family of magnetic van-der-Waals materials (M denotes a first row transition metal and X either S or Se) are currently the subject of broad and intense attention, but the vanadium compounds have until this point not been studied beyond their basic properties. We observe insulating variable-range-hopping type resistivity in V$_{0.9}$PS$_3$, with a gradual increase in effective dimensionality with increasing pressure, followed by a transition to a metallic resistivity temperature dependence between 112 and 124 kbar. The metallic state additionally shows a low-temperature upturn we tentatively attribute to the Kondo Effect. A gradual structural distortion is seen between 26-80 kbar, but no structural change at higher pressures corresponding to the insulator-metal transition. We conclude that the insulator-metal transition occurs in the absence of any distortions to the lattice - an isostructural Mott transition in a new class of two-dimensional material, and in strong contrast to the behavior of the other MPX$_3$ compounds.