Fig. 5: Numerical modelling of the electronic structure of 1T-TaS2.
From: Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered 1T-TaS2
a, b Arrangements of the David-star-shaped clusters (only Ta atoms are shown) in successive layers of commensurately distorted 1T-TaS2, considered for our density functional theory (DFT) calculations. After ref. 24, we denote these stacking configurations as A a and L b. The red arrows join the Ta atoms sharing the same lateral position. The top–right sections of both panels display the first Brillouin zones for the corresponding lattices in relation to the first Brillouin zone for the undistorted 1T-TaS2. c, d The respective electronic band structures and densities of states (DOS) predicted by the DFT calculations for relaxed lattices and with the on-site electron–electron interaction energy U = 2.41 eV. The directions traced in the reciprocal space are marked in a and b. Each colour stands for a different band. e, f The respective Fermi surfaces. The extended open sheets in both cases indicate a quasi-one-dimensional character of the electronic structures. g Conductivity ellipsoid calculated from the electron energy dispersion near the Fermi surface (i.e., assuming isotropic relaxation time), in relation to the crystal structure for the L stacking. The longest axis of the ellipsoid indicates the direction of the highest conductivity. The ellipsoid is slightly slanted (~8°) with respect to the line connecting the centres of two nearest-neighbour clusters in two adjacent layers. The ratios of the highest conductivity to the conductivities along the two shorter principal axes of the ellipsoid are ~13 and 5.
