Spin polarization in the Hubbard model with Rashba spin-orbit coupling on a ladder

TL;DR

This study investigates how electron interactions and Rashba spin-orbit coupling influence spin polarization and currents in a ladder model, revealing enhanced spin accumulation and antiferromagnetic order with potential spintronic applications.

Contribution

It provides new insights into the interplay between Coulomb repulsion and Rashba spin-orbit coupling in ladder systems using numerical methods.

Findings

Maximum spin-flipping current at intermediate RSOC values

Suppression of spin-flipping current with increasing Hubbard U

Enhanced spin accumulation and antiferromagnetic order due to interactions

Abstract

The competition between on-site Coulomb repulsion and Rashba spin-orbit coupling (RSOC) is studied on two-leg ladders by numerical techniques. By studying persistent currents in closed rings by exact diagonalization, it is found that the contribution to the current due to the RSOC V_{SO}, for a fixed value of the Hubbard repulsion U reaches a maximum at intermediate values of V_{SO}. By increasing the repulsive Hubbard coupling U, this spin-flipping current is suppressed and eventually it becomes opposite to the spin-conserving current. The main result is that the spin accumulation defined as the relative spin polarization between the two legs of the ladder is enhanced by U. Similar results for this Hubbard-Rashba model are observed for a completely different setup in which two halves of the ladders are connected to a voltage bias and the ensuing time-dependent regime is studied by the density matrix-renormalization group technique. It is also interesting a combined effect between V_{SO} and U leading to a strong enhancement of antiferromagnetic order which in turn may explain the observed behavior of the spin-flipping current. The implications of this enhancement of the spin-Hall effect with electron correlations for spintronic devices is discussed.