Yuma Kitagawa | Searcharxiv

arXiv2023

Transport through a monolayer-tube junction: sheet-to-tube spin current in silicene

A method is developed to calculate the electron flow between an atomic monolayer sheet and a tube with use of tunneling matrix elements between monolayer sheets and applied to the spin current from monolayer silicene with sublattice-staggered current-induced spin polarization to silicene tube. Calculated sheet-to-tube spin current exhibits an oscillation as a function of the tube circumferential length since the Fermi points in the tube cross the Fermi circle in the sheet. It is also shown that the spin current with spin in the out-of-plane direction, which is absent in the sheet-sheet junction (including twisted sheets) with the $C_3$ rotational symmetry, appears in an oscillating form owing to the broken $C_3$ symmetry in the tube-sheet junction.

cond-mat.mes-hall↗

arXiv2023

Antiparallel spin polarization and spin current induced by thermal current and locally-broken inversion symmetry in a double-quantum-well structure

Generating a nonequilibrium spin polarization with a driving force has been first realized by the electric current in a system with broken inversion symmetry and extended to that induced by the thermal current and that appearing in an inversion-symmetric system with locally-broken inversion symmetry. This paper theoretically explores the spin polarization generated by the thermal current and the locally-broken inversion symmetry in a symmetric double-quantum-well structure (DQWS). This thermally-induced spin polarization (TISP) appears in the antiparallel configuration with the TISP of two wells in opposite directions. The calculation using the Boltzmann equation in the relaxation-time approximation under the condition of zero charge current shows that the local TISP exhibits the maximum at a finite Rashba spin-orbit interaction when the electron density is fixed. This is because the local TISP in the DQWS is enhanced at the chemical potential near the bottom of the first-excited subband. This enhancement also occurs in a single quantum well with globally-broken inversion symmetry. Another finding is that the maximum of the local TISP appears at a nonzero interwell coupling. The spin current by the diffusion of the local TISP into an adjacent electrode is also calculated.

cond-mat.mes-hall↗