Speaker
Description
Recent experiments in twisted bilayer MoTe2 (t-MoTe2) have uncovered many correlation-driven phases at various hole filling factors. The phases like fractional Chern Insulator, quantum anomalous Hall phase, superconducting states, and generalized Wigner crystal phase have been confirmed by multiple experimental studies. The majority of these phases are observed at either integer fillings or fractional fillings less than 1. However, one of the recent experimental findings shows correlated insulating states at fillings 4/3 and 3/2 for samples with 3.83o twist, which were interpreted as possible charge density wave states.
In our work, we have focused on revealing the exact nature of the insulating states at 4/3 and 3/2 fillings. We have studied the 2-band interacting model of the system to investigate the charge and spin order of these states. We employed unrestricted Hartree-Fock formalism in the real-space, allowing for spontaneous symmetry breaking without imposing any predefined supercell structure.
Our detailed analysis shows that the t-MoTe2 system possesses a very rich phase diagram in terms of general Wigner crystal phases as a function of twist angle and the strength of the applied displacement field. While the majority of the phase space is dominated by various √3x√3 ordered states, 2x2 ordered states appear when the displacement field is negligible. We found that the small and large twist systems are in the inter-valley coherent state (IVC) and valley polarized state (VP), respectively. The IVC to VP transition happens at 1.5o twist for both 4/3 and 3/2 fillings. The transition between any two ordered states can be tracked by the evolution of quantities like layer-polarization, spin-polarization, total energy, etc. Analysis of such quantities shows that all the transitions in our phase diagram are first-order in nature.