V$_5$S$_8$: a Kondo lattice based on intercalation of van der Waals layered transition metal dichalcogenide

TL;DR

This paper reports the creation of a Kondo lattice in a 2D transition metal dichalcogenide via intercalation, demonstrating strong electron correlations and Kondo physics in ultra-thin films, opening new avenues for correlated 2D materials.

Contribution

It introduces a novel method to induce strong electronic correlations in 2D materials through intercalation, specifically realizing a $d$-electron Kondo lattice in V$_5$S$_8$.

Findings

Observation of a large Sommerfeld coefficient indicating strong correlations

Detection of Kondo lattice behavior through transport measurements

Persistence of Kondo physics in ultra-thin films

Abstract

Since the discovery of graphene, a tremendous amount of two dimensional (2D) materials have surfaced. Their electronic properties can usually be well understood without considering correlations between electrons. On the other hand, strong electronic correlations are known to give rise to a variety of exotic properties and new quantum phases, for instance, high temperature superconductivity, heavy fermions and quantum spin liquids. The study of these phenomena has been one of the main focuses of condensed matter physics. There is a strong incentive to introduce electronic correlations into 2D materials. Via intercalating a van der Waals layered compound VS$_2$, we show an emergence of a Kondo lattice, an extensively studied strongly correlated system, by magnetic, specific heat, electrical and thermoelectric transport studies. In particular, an exceptionally large Sommerfeld coefficient, 440 mJ$\cdot$K$^{-2}\cdot$mol$^{-1}$, indicates a strong electron correlation. The obtained Kadowaki-Woods ratio, $2.7\times 10^{-6}$ $\mu\Omega\cdot$cm$\cdot$mol$^2\cdot$K$^2\cdot$mJ$^{-2}$, also supports the strong electron-electron interaction. The temperature dependence of the resistivity and thermopower corroborate the Kondo lattice picture. The intercalated compound is one of a few rare examples of $d$-electron Kondo lattices. We further show that the Kondo physics persists in ultra-thin films. This work thus demonstrates a route to generate strong correlations in 2D materials.