Emergent quantum phenomena in two-dimensional 1T-TaS2

TL;DR

This review discusses how strong electron correlations in 2D 1T-TaS2 lead to various quantum states like Mott insulators, charge density waves, and quantum spin liquids, emphasizing experimental insights and control methods.

Contribution

It synthesizes recent experimental findings on quantum states in 2D 1T-TaS2, highlighting the effects of dimensionality and external stimuli on its electronic properties.

Findings

Identification of signatures of quantum spin liquid in electronic spectra

Demonstration of external control over quantum states via gating and light

Insights into the role of Kondo effect in spinon detection

Abstract

Strong electron correlation drives 1T-TaS2 from a half-filled metallic state into a Mott insulating phase, coexisting with a charge density wave at low temperatures. Under external stimuli such as pressure or ionic gating, superconductivity emerges in 1T-TaS2, exhibiting an intricate relationship of competition and coexistence with the charge density wave order. In the two-dimensional (2D) limit, enhanced quantum fluctuations can stabilize a quantum spin liquid (QSL) state in the Mott insulator. This review summarizes recent advances in understanding these quantum states in 2D 1T-TaS2 from the perspective of angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM), with a focus on the dimensionality effect on its electronic structure. We outline the signatures of QSL state in electronic spectra and discuss how this state can be revealed in the family of this material through experimental approaches beyond conventional probes such as neutron scattering. The role of Kondo effect in detecting spinon excitations is further discussed. Finally, we suggest future experimental directions and highlight how external perturbations such as gating and light excitation offer versatile pathways to control and exploit these intertwined quantum states.