Dynamical mean field theory of moiré bilayer transition metal dichalcogenides: phase diagram, resistivity, and quantum criticality

Abstract

We present a comprehensive dynamical mean field study of the moiré Hubbard model, which is believed to represent the physics of moiré bilayer transition metal dichalcogenides. In these materials, important aspects of the band structure including the bandwidth and the order and location of van Hove singularities can be tuned by varying the interlayer potential. We present a magnetic and metal-insulator phase diagram and a detailed study of the dependence of the resistivity on temperature, band filling and interlayer potential. We find that transport displays Fermi liquid, strange metal and quantum critical behaviors in distinct regions of the phase diagram. We show how magnetic order affects the resistivity. Our results elucidate the physics of the correlated states and the metal-insulator continuous transition recently observed in twisted homobilayer WSe2 and heterobilayer MoTe2/WSe2 experiments.

In situ controllable magnetic phases in doped twisted bilayer transition-metal dichalcogenides

“…At a 5.1 • twist, superconductivity has been observed with a critical temperature of T c ≈ 3K [9] . These twist angles correspond to a parameter regime where the onsite repulsion is comparable to the bandwidth [7,10], implying strong magnetic correlations. For physically realizable model parameters, super-exchange processes are predicted to favor anti-ferromagnetism [7,11], and so this scenario bears a striking similarity to the cuprate superconductors [12].…”

“…For physically realizable model parameters, super-exchange processes are predicted to favor anti-ferromagnetism [7,11], and so this scenario bears a striking similarity to the cuprate superconductors [12]. Recently, strange metal behavior was also predicted theoretically using dynamic mean-field theory [10].…”

“…By contrast, the onsite repulsion changes by less that a factor 2 in the same interval, thus permitting the relative interaction U/t to change dramatically. At θ = 4 − 5 • , the hopping integral has been estimated to |t| ∼ 100K while U/t ∼ 8 [10], and so the regime θ ≈ 1 • corresponds to extremely large onsite interactions with a corresponding suppression of super-exchange processes. Higher order corrections to the model (1) consist of longer range hopping and also non-local repulsive interactions.…”

“…While the results reported here were obtained in the strongcoupling limit, they remain relevant for physical parameter regimes of the TTMD's. For example, at twist-angles of θ = 4 − 5 • , estimates of effective model parameters yield |t| ∼ 100K and U/t ∼ 8 [10]. If the hopping integral is shrunk by two orders of magnitude via the twist-angle, and the onsite repulsion changes by less than a factor 2 [7], then this gives a super-exchange J/t ∼ 4t/U ∼ 100 and t ∼ 1K.…”

Tunable Stripe Order and Weak Superconductivity in the Moiré Hubbard Model

“…Exotic emergent phenomena including correlated insulating states [1,2], quantum critically and tunable metal-insulator transitions (MIT) [3,4] have been recently realized in the twisted WSe 2 system, a typical class of transition metal dichalcogenides. The low energy physics of twisted WSe 2 is well captured by the so-called moiré Hubbard model, a variant of the standard triangular lattice Hubbard model in which the electron hopping amplitude acquires a spin-dependent phase (pseudomagnetic field) [5][6][7][8][9][10]. The Hamiltonian H of the moiré Hubbard model is the sum of kinetic (H 0 ) and interaction (H I ) terms with H 0 = −t σ=↑,↓ r,j=1,2,3 e iσφ c † r+aj ,σ c r,σ + h.c. , (1) and H I = U r n r↑ n r↓ is the standard onsite repulsive Hubbard interaction.…”