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Michael M. Scherer
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Dirac materials
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- Description:
- Recent experiments on twisted double bilayer tungsten diselenide have demonstrated that moir\'e semiconductors can be used to realize a relativistic Mott transition, i.e., a quantum phase transition from a Dirac semimetal to a correlated insulating state, by twist-angle tuning. In addition, signatures of van Hove singularities were observed in the material's moir\'e valence bands, suggesting further potential for the emergence of strongly-correlated states in this moir\'e semiconductor. , Based on a Bistritzer-MacDonald-type continuum model, we provide a detailed analysis of the twist-angle dependence of the system's moir\'e valence band structure, focussing on both, the evolution of the Dirac excitations and the Fermi-surface structure with its Lifshitz transitions across the van Hove fillings. We exhibit that the twist angle can be used to band engineer a high-order van Hove singularity with power-law exponent~$-1/4$ in the density of states, which can be accessed by gate tuning of the hole filling., We then study the magnetic phase diagram of an effective Hubbard model for twisted double bilayer tungsten diselenide on the effective moir\'e honeycomb superlattice with tight-binding parameters fitted to the two topmost bands of the continuum model. To that end, we employ a self-consistent Hartree-Fock mean-field approach in real space. Fixing the angle-dependent Hubbard interaction based on the experimental findings, we explore a broad parameter range of twist angle, filling, and temperature., We find a rich variety of magnetic states that we expect to be accessible in future experiments by twist or gate tuning, including, e.g., a non-coplanar spin-density wave with non-zero spin chirality and a half-metallic uniaxial spin-density wave., In this dataset, we provide the angle-dependent parameters of the effective honeycomb-lattice Hubbard model for twisted double bilayer tungsten diselenide in ABBA stacking order., Based on a Bistritzer-MacDonald-type continuum model, we have calculated an effective honeycomb-lattice Hubbard model with tight-binding parameters fitted to the two topmost bands. The model parameters are twist-angle dependent and we provide data for all angles between 1.00 degree and 4.18 degrees in steps of 0.02 degrees. We include n-th-nearest neighbor hopping amplitudes, 'tn', up to the 10th nearest neighbor, i.e., t1,..., t10, and an additional energy offset 'E0' to match the band energies of the continuum model. We also give our estimate for the angle-dependent on-site Hubbard interaction 'U'. All quantities are given in units of meV., and For a chosen twist angle the parameters provided in our data file uniquely define an effective honeycomb-lattice Hubbard model that describes the two topmost Gamma-valley moir\'e valence bands of twisted double bilayer tungsten diselende in ABBA stacking order. The model is then a starting point for quantum-many-body calculations. In the accompanying publication to this data set, we use the model to calculate the magnetic phase diagram employing an unrestricted Hartree-Fock mean-field approach in real space.
- Keyword:
- Moiré materials, Twisted double bilayer tungsten diselenide, Relativistic Mott transition, 2D materials, Magnetic phase diagram, Band-structure calculations, Honeycomb-lattice Hubbard model, Van Hove Singularity, Hartree-Fock mean-field, Strongly-correlated electron systems, and Dirac materials
- Date Uploaded:
- 2025-08-28
- Date Modified:
- 2025-09-12
- License:
- Creative Commons BY-NC-SA Attribution-NonCommercial-ShareAlike 4.0 International
- Resource Type:
- Dataset