Tuning Quantum Phase Transitions at Half Filling in 3L-MoTe_{2}/WSe_{2} Moiré Superlattices

Abstract

Many sought-after exotic states of matter are known to emerge close to quantum phase transitions, such as quantum spin liquids 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 moiré superlattices formed between trilayer MoTe_{2} and monolayer WSe_{2} (3L-MoTe_{2}/WSe_{2}). Through transport measurements, we observe an electronic analog of the Pomeranchuk effect at half filling of the first moiré subband, where increasing temperature paradoxically enhances charge localization. At low temperatures the system 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 under 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-field-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.