Fig. 1: Shift current conductivity of a minimal k · p model.
From: Colossal switchable photocurrents in topological Janus transition metal dichalcogenides
The shift current conductivity \(\sigma _{xx}^x\) for the model Hamiltonian H(k) = d(k) · σ + μσx, where \({\mathbf{d}}\left( {\mathbf{k}} \right) = [ {Ak_x,\,Ak_y,M - B( {k_x^2 + k_y^2} )}]\) and σ = [σx,σy,σz] are Pauli matrices. a M is varied. For positive and negative M with the same absolute value, \(|\sigma _{xx}^x|\) is larger when M is positive due to band inversion. A = 2, B = 1, μ = 0.1 is used. Blue and red solid curves are \(\sigma _{xx}^x\) for M > 0 and M < 0, respectively. For better visibility, the red solid curve is flipped (red dashed curve, with an extra minus sign) to be compared with the blue curve. b μ is varied. \(\sigma _{xx}^x\) scales approximately linearly with μ, which determines the strength of inversion symmetry breaking. A = 2, B = 1, M = 1 is used.
