Spin transport through a spin-1/2 XXZ chain contacted to fermionic leads

Abstract

We employ matrix-product state techniques to numerically study the zero-temperature spin transport in a finite spin-1/2 XXZ chain coupled to fermionic leads with a spin bias voltage. Current-voltage characteristics are calculated for parameters corresponding to the gapless XY phase and the gapped Néel phase. In both cases, the low-bias spin current is strongly suppressed unless the parameters of the model are fine-tuned. For the XY phase, this corresponds to a conducting fixed point where the conductance agrees with the Luttinger-liquid prediction. In the Néel phase, fine-tuning the parameters similarly leads to an unsuppressed spin current with a linear current-voltage characteristic at low bias voltages. However, with increasing the bias voltage, there occurs a sharp crossover to a region where a current-voltage characteristic is no longer linear and the smaller differential conductance is observed. We furthermore show that the parameters maximizing the spin current minimize the Friedel oscillations at the interface, in agreement with the previous analyses of the charge current for inhomogeneous Hubbard and spinless fermion chains.

9 pages, 8 figures, minor revisions

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• Non-equilibrium non-Markovian steady-states in open quantum many-body systems: Persistent oscillations in Heisenberg quantum spin chains
• Theoretical analysis of FMR-driven spin pumping current and its properties via Self-Consistent Harmonic Approximation
• Driving XXZ spin chains: Magnetic-field and boundary effects
• Generation of current vortex by spin current in Rashba systems
• Topological phase and lattice structures in spin chain models
• Density-matrix renormalization group study of the linear conductance in quantum wires coupled to interacting leads or phonons
• Block-Lanczos density-matrix renormalization-group approach to spin transport in Heisenberg chains coupled to leads