Pomeranchuk Effect and Tunable Quantum Phase Transitions in 3L-MoTe2/WSe2

TL;DR

This paper explores tunable quantum phase transitions and correlation effects in trilayer MoTe2/WSe2 moiré superlattices, revealing the Pomeranchuk effect, Lifshitz transition, and quantum criticality through electric transport measurements.

Contribution

It demonstrates the tunability of quantum phase transitions in 3L-MoTe2/WSe2, including the observation of the Pomeranchuk effect and Lifshitz transition, and maps the quantum phase diagram.

Findings

Observation of Pomeranchuk effect at half filling

Electric and magnetic field-induced Lifshitz and metal-insulator transitions

Identification of a tricritical point and quantum criticality

Abstract

Many sought-after exotic states of matter are known to emerge close to quantum phase transitions, such as quantum spin liquids (QSL) and unconventional superconductivity. It is thus desirable to experimentally explore systems that can be continuously tuned across these transitions. Here, we demonstrate such tunability and the electronic correlation effects in triangular moir\'e superlattices formed between trilayer MoTe$_2$ and monolayer WSe$_2$ (3L-MoTe$_2$/WSe$_2$). Through electric transport measurements, we firmly establish the Pomeranchuk effect observed at half filling of the first moir\'e subband, where increasing temperature paradoxically enhances charge localization. The system simultaneously exhibits the characteristic of a Fermi liquid with strongly renormalized effective mass, suggesting a correlated metal state. The state is highly susceptible to out-of-plane electric and magnetic fields, which induce a Lifshitz transition and a metal-insulator transition (MIT), respectively. It enables identification of a tricritical point in the quantum phase diagram at the base temperature. We explain the Lifshitz transition in terms of interlayer charge transfer by applying the vertical electric field, which leads to the emergence of a new Fermi surface and immediate suppression of the Pomeranchuk effect. The existence of quantum criticality in the magnetic filed induced MIT is supported by scaling behaviors of the resistance. Our work shows the 3L-MoTe$_2$/WSe$_2$ lies in the vicinity to the MIT point of the triangular lattice Hubbard model, rendering it a unique system to manifest the rich correlation effects at an intermediate interaction strength.