One-directional polarization transport in electron/nuclear spin chains with loss and gain

BUSSANDRI, SANTIAGO; ZANGARA, PABLO R.; ACOSTA, RODOLFO H.; MERILES, CARLOS A.

Physical Review B

APS

Año: 2021 vol. 103

2469-9950

Understanding the joint dynamics of electron and nuclear spins is central to core concepts in solid-state magnetic resonance such as spin-lattice relaxation and dynamic nuclear polarization, but a generalization that capitalizes on competing polarization loss and gain channels is still lacking. Here, we study theoretically the non-Hermitian dynamics of hybrid electron/nuclear spin systems in the simultaneous presence of electron spin pumping and spin-lattice relaxation. Focusing on periodic, one-dimensional chains, we find that, by adjusting the electron spin pumping to a critical level, it is possible to steer the flow of nuclear polarization to create site-dependent distributions where either end of the array polarizes in opposite ways, irrespective of the initial state. By contrast, we show that ring-like patterns?where the limit nuclear polarization is uniform?exhibit a non-decaying, externally driven nuclear spin current. Interestingly, cyclic magnetic field modulation can render these processes largely robust to defects in the chain, a response featuring some interesting similarities?and differences?with recent findings in other non-Hermitian physical platforms.