Global Spin Current in Excitonic Phases of the Two-Band Hubbard Model*

It has recently been pointed out that the k-space spin texture may emerge in the doped excitonic phase of a two-orbital Hubbard model containing the cross-hopping terms with certain symmetry [1-3]. Thanks to the spontaneous breaking of the inversion symmetry by the excitonic phase transition, the global spin current perpendicular to the applied electric field is induced by the spin-dependent off-diagonal component of the Drude weight. The mechanism is quite different from the conventional one originated from the spin Hall effect where a spin-orbit coupling plays an essential role, and thus our result gives a new route to generate a spin current.
[1] J. Kuneš and D. Geffroy, Phys. Rev. Lett. 116, 256403 (2016).
[2] D. Geffroy, A. Hariki, and J. Kuneš, Phys. Rev. B 97, 155114 (2018).
[3] H. Nishida, S. Miyakoshi, T. Kaneko, K. Sugimoto, and Y. Ohta, Phys. Rev. B 99, 035119 (2019).