arXiv subjects

Hai Meng

Publications and source records attributed to Hai Meng.

3 recordsLinked to original sources

arXiv2026

Supermoir\'e Reconstruction and Topological Mosaics in Twisted Trilayer WSe$_2$ and MoTe$_2$

We investigate lattice relaxation and band structures of helical and alternating twisted trilayer WSe$_2$ and MoTe$_2$ using machine-learning force fields and large-scale ab initio calculations. Interference between the two bilayer moir\'e lattices generates a supermoir\'e lattice that, upon relaxation, reconstructs into a few dominant domain types with locally commensurate bilayer moir\'e lattices. Because the systems lack $C_{2z}$ symmetry, domains otherwise related by this symmetry become energetically and topologically distinct, unlike in twisted trilayer graphene. Band structure calculations show that the topmost valence bands originate from the $K$ ($K'$) valleys and carry domain-dependent valley Chern numbers. The resulting supermoir\'e lattice hosts a mosaic of topologically inequivalent domains, offering a platform for exploring correlated and topological physics.

cond-mat.mes-hall↗

arXiv2026

Supermoir\'e Chern mosaic in helical trilayer WSe2

Helically twisted multilayers offer access to moir\'e physics beyond the single-superlattice paradigm, yet their correlated and topological transport properties remain largely unexplored in semiconductor moir\'e materials. Here we report magnetotransport measurements of helical trilayer WSe2, in which two coupled moir\'e patterns relax into a supermoir\'e landscape composed of inequivalent local topological domains with distinct electronic structures and unequal spatial areas. By electrostatic tuning, we identify a trilayer-hybridized regime where interactions and real-space reconstruction combine to generate a plethora of magnetic and topological states absent in the twisted bilayers. At moir\'e filling factor $\nu$ = -1, we observe a ferromagnetic insulating state that is robust against magnetic field and accompanied by a non-quantized anomalous Hall response ~-4 kOhms. This behaviour is consistent with a time-reversal-symmetry-breaking supermoir\'e Chern mosaic, in which the Hall response arises from the non-cancelling contributions of local domains with opposite Chern character arranged by the relaxed structure. Under strong magnetic fields, a symmetry-broken Chern insulating state (C = 1) emerges near $\nu$ = -2/3, displaying a much larger positive Hall response together with strongly enhanced longitudinal resistance, suggestive of field-reconstructed topological minibands and domain-boundary scattering. These results establish relaxed supermoir\'e semiconductor trilayers as a platform for spatially organized magnetism and topology beyond the bilayer limit.

cond-mat.str-el↗

arXiv2022

Commensurate and incommensurate double moiré interference in twisted trilayer graphene

Twisted graphene multi-layers have been recently demonstrated to share several correlation-driven behaviours with twisted bilayer graphene. In general, the van Hove singularities (VHSs) can be used as a proxy of the tendency for correlated behaviours. In this paper, we adopt an atomistic method by combining tight-binding method with the semi-classical molecular dynamics to investigate the electronic structures of twisted trilayer graphene (TTG) with two independent twist angles. The two independent twist angles can lead to the interference of the moiré patterns forming a variety of commensurate/incommensurate complex supermoiré patterns. In particular, the lattice relaxation, twist angle and angle disorder effects on the VHS are discussed. We find that the lattice relaxation significantly influence the position and magnitude of the VHSs. In the supermoiré TTG, the moiré interference provides constructive or destructive effects depending on the relative twist angle. By modulating the two independent twist angles, novel superstructures, for instance, the Kagome-like lattice, could constructed via the moiré pattern. Moreover, we demonstrate that a slight change in twist angles (angle disorder) provides a significant suppression of the peak of the VHSs. Apart from the moiré length, the evolution of the VHSs and the LDOS mapping in real space could be used to identify the twist angles in the complicated TTG. In practice, our work could provide a guide for exploring the flat band behaviours in the supermoiré TTG experimentally.

cond-mat.mes-hall↗