2025/09/19 by Valéria M. Mattiello, Mattiello, Valéria M., Victor L. Quito +3
Physics and Astronomy · #Disordered Systems and Neural Networks (cond-mat.dis-nn) #FOS: Physical sciences #Nonlinear Waves and Solitons #Quantum Mechanics and Non-Hermitian Physics #Quantum chaos and dynamical systems #Strongly Correlated Electrons (cond-mat.str-el)
paper · pdf · doi:10.48550/arxiv.2509.16309
openalex publication_date 2025/09/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present an asymptotically exact solution of a paradigmatic non-Hermitian model: the disordered interacting fermionic Hatano-Nelson model, or equivalently, the non-Hermitian spin-1/2 XXZ model. We use a renormalization group method suited for disordered systems and show that non-Hermitian couplings are relevant perturbations to the Hermitian model, which ultimately leads to a quantum-to-classical crossover. The ground state of the model consists of a collection of strongly coupled pairs of spins of arbitrary size at random positions which, unlike the Hermitian case, do not form singlets, but a mixture of the singlet and the M=0 triplet state. As a result, the magnetic susceptibility in the x,y-directions becomes negative and diverges at a finite small temperature. Additionally, in sharp contrast to the ln(L) increase observed in disordered Hermitian chains, the entanglement entropy of a partition of size L saturates for large L, as the strongly coupled pairs become classical and stop contributing at large length scales.