Helical currents in metallic Rashba strips

I. J. HAMAD; C. J. GAZZA; J. A. RIERA

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Año: 2016 vol. 93

0163-1829

We study the texture of helical currents in metallic planar strips in the presence of Rashba spin-orbit coupling(RSOC) on the lattice at zero temperature. In the noninteracting case and in the absence of external electromagneticsources, we determine, by exact numerical diagonalization of the single-particle Hamiltonian, the distributionacross the strip section of these Rashba helical currents (RHC) as well as their sign oscillation, as a functionof the RSOC strength, strip width, electron filling, and strip boundary conditions. Then, we study the effectsof charge currents introduced into the system by an Aharonov-Bohm flux for the case of rings or by a voltagebias in the case of open strips. The former setup is studied by variational Monte Carlo, and the latter by thetime-dependent density-matrix renormalization-group technique. Particularly for strips formed by two, three,and four coupled chains, we show how these RHC vary in the presence of such induced charge current, and howtheir differences between spin-up and spin-down electron currents on each chain help to explain the distributionacross the strip of charge currents, both of the spin-conserving and the spin-flipping types. We also predict theappearance of polarized charge currents on each chain. Finally, we show that these Rashba helical currents andtheir derived features remain in the presence of an on-site Hubbard repulsion as long as the system remainsmetallic, at quarter filling, and even at half filling where a Mott-Hubbard metal-insulator transition occurs forlarge Hubbard repulsion.