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arXiv · 2006.01324

Dynamic magnetization in non-Hermitian quantum spin system

X. Z. Zhang·L. Jin·Z. Song
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Abstract

We report a global effect induced by the local complex field, associated with the spin-exchange interaction. High-order exceptional point up to ($N+1$)-level coalescence is created at the critical local complex field applied to the $N$-size quantum spin chain. The ($N+1$)-order coalescent level is a saturated ferromagnetic ground state in the isotropic spin system. Remarkably, the final state always approaches the ground state for an arbitrary initial state with any number of spin flips; even if the initial state is orthogonal to the ground state. Furthermore, the switch of macroscopic magnetization is solely driven by the time and forms a hysteresis loop in the time domain. The retentivity and coercivity of the hysteresis loop mainly rely on the non-Hermiticity. Our findings highlight the cooperation of non-Hermiticity and the interaction in quantum spin system, suggest a dynamical framework to realize magnetization, and thus pave the way for the non-Hermitian quantum spin system.

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X. Z. Zhang, L. Jin, Z. Song. 2020-06-02. Dynamic magnetization in non-Hermitian quantum spin system. https://doi.org/10.1103/physrevb.101.224301

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