Kavli Affiliate: Zheng Zhu
| First 5 Authors: Mingjie Zhang, Xuan Zhao, Kenji Watanabe, Takashi Taniguchi, Zheng Zhu
| Summary:
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.
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