SFB 1238 | November 04, 14:30
Hidden antiferromagnetism, persistent valley fluctuations, and $U(6)$ crossovers in triangular-lattice $M$-point moir\'e materials via determinantal quantum Monte Carlo
A new moiré material platform was recently proposed based on twisting two-dimensional atomic monolayers whose low-energy states lie at the three $M$-points of the Brillouin zone. Continuum and *ab initio* modeling suggest that electrons in the conduction bands of these materials realize three-valley Hubbard models with valley-selective, quasi-one-dimensional hopping. Remarkably, the onsite Hubbard repulsion is almost $U(6)$-symmetric without fine-tuning.
In this talk, I will discuss how this class of systems naturally admits sign-free determinantal Quantum Monte Carlo simulations at a filling of three electrons per moiré unit cell, and present results for the phase diagram at various interaction strengths and $U(6)$-breaking anisotropies. For near-isotropic interactions, as relevant to, e.g., AA-stacked twisted SnSe$_2$, we find an extended intermediate-coupling regime in which local-moment formation and itinerancy compete. The crossover to a putative low-temperature ordered state can be understood in terms of fluctuating $U(6)$ local moments. Finally, I will discuss to what extent these features persist beyond the idealized sign-problem-free limit.
MPI-PKS
PH2
Contact: Urban Seifert