First Order Quantum Phase Transition in the Hybrid Metal-Mott Insulator Transition Metal Dichalcogenide 4Hb-TaS2

TL;DR

This study uncovers a first order quantum phase transition in the compound 4Hb-TaS2, toggling between a Kondo cluster state and a flat band state, controllable by electric field, temperature, and interlayer coupling, revealing new insights into correlated electronic phases.

Contribution

It demonstrates a reversible, electric-field-induced quantum phase transition in a hybrid metal-Mott insulator system, advancing understanding of strongly correlated phases and quantum criticality.

Findings

Identified a first order quantum phase transition in 4Hb-TaS2.

Showed the transition can be controlled by electric field, temperature, and interlayer coupling.

Observed hysteresis and discontinuous spectral changes at the transition.

Abstract

Coupling together distinct correlated and topologically non-trivial electronic phases of matter can potentially induce novel electronic orders and phase transitions among them. Transition metal dichalcogenide compounds serve as a bedrock for exploration of such hybrid systems. They host a variety of exotic electronic phases and their Van der Waals nature enables to admix them, either by exfoliation and stacking or by stoichiometric growth, and thereby induce novel correlated complexes. Here we investigate the compound 4Hb-TaS$_2$ that interleaves the Mott-insulating state of 1T-TaS$_2$ and the putative spin liquid it hosts together with the metallic state of 2H-TaS$_2$ and the low temperature superconducting phase it harbors. We reveal a thermodynamic phase diagram that hosts a first order quantum phase transition between a correlated Kondo cluster state and a flat band state in which the Kondo cluster becomes depleted. We demonstrate that this intrinsic transition can be induced by an electric field and temperature as well as by manipulation of the interlayer coupling with the probe tip, hence allowing to reversibly toggle between the Kondo cluster and the flat band states. The phase transition is manifested by a discontinuous change of the complete electronic spectrum accompanied by hysteresis and low frequency noise. We find that the shape of the transition line in the phase diagram is determined by the local compressibility and the entropy of the two electronic states. Our findings set such heterogeneous structures as an exciting platform for systematic investigation and manipulation of Mott-metal transitions and strongly correlated phases and quantum phase transitions therein.