Fig. 2: Electronic structure and phase diagram of CCDW 1T-TaSe2 systems.
From: Deconfinement of Mott localized electrons into topological and spin–orbit-coupled Dirac fermions
a Band structures of CCDW 1T-TaSe2 monolayer (left) in comparison to honeycomb-stacked non-twisted CCDW 1T-TaSe2 bilayer (right). Bottom panels show a zoom around the Fermi level EF. The red and dashed blue lines mark the DFT low-energy bands without and with SOC included, respectively. From the flat band near EF in the monolayer (red solid line, bandwidth ≈ 14 meV) two dispersive bands with a bandwidth ≈ 200 meV emerge in the bilayer case. The bilayer bands exhibit Dirac points in the Brillouin zone corners, K and K'. b Influence of extrinsic Semenoff mass terms ΔM on the low-energy band structure. The sublattice character is color coded. The system changes from QSH to trivial band insulator at ΔM = 0.82 meV, which corresponds to a vertical electric field of Ez ≈ 0.5 mV Å−1. c Quasi-particle weight Z for non-twisted CCDW 1T-TaSe2 bilayer calculated with DMFT and TPSC. Both approaches place the system consistently in the moderately correlated regime Z ≈ 0.75 at all calculated temperatures. d Temperature-dependent antiferromagnetic correlation length ξAFM and inverse static spin susceptibilities of non-twisted CCDW 1T-TaSe2 bilayer at wave vector q = 0 as calculated with TPSC. The intra-sublattice (1/χAA = 1/χBB) and inter-sublattice (1/χAB) elements of the inverse susceptibility at wave number q = 0 are shown. e Schematic phase diagram of honeycomb-stacked non-twisted CCDW 1T-TaSe2 bilayer as a function of extrinsic Semenoff mass ΔM and interaction strength U. The region accessible for non-twisted CCDW 1T-TaSe2 bilayer through tuning with external electric fields is highlighted. The transition from QSH to band insulator is a continuous transition at small U (dashed line) and a first-order transition at larger U (solid line). The red area in the quantum spin Hall region indicates the increasing many-body character of this phase.
