arXiv subjects

Ali Tozar

Publications and source records attributed to Ali Tozar.

4 recordsLinked to original sources

arXiv2025

Interaction-Induced Breakdown of Anderson Localization: Thermodynamic Segregation disguised as the Skin Effect

We investigate the interplay between strong disorder and repulsive interactions in the one-dimensional Fermi-Hubbard model under open boundary conditions. While uncorrelated disorder is widely accepted to localize all single-particle eigenstates, a phenomenon typically reinforced by interactions in the Many-Body Localization (MBL) regime, we report a counter-intuitive breakdown of this paradigm. We demonstrate that strong repulsive interactions can overcome disorder-induced localization, driving the system into a macroscopically segregated phase where spin species accumulate at opposite boundaries. Although this boundary accumulation phenomenologically mimics the Non-Hermitian Skin Effect (NHSE) observed in non-reciprocal systems, our comprehensive analysis reveals a fundamentally different origin. By performing a rigorous control experiment in the Hermitian limit, we prove that the segregation persists without non-reciprocity, identifying many-body energy minimization as the primary driver. This "interaction-induced segregation" manifests as a sharp thermodynamic crossover, characterized by a divergent energy susceptibility, challenging the conventional understanding of disorder-interaction competition in open quantum systems.

cond-mat.str-el↗

arXiv2025

Symmetry-Protected Bipolar Skin Effect and its Topological Breakdown in Disordered Non-Hermitian Systems

The interplay between non-Hermitian topology and disorder remains a central puzzle in open quantum systems. While the non-Hermitian skin effect (NHSE) is known to be robust against weak perturbations, its fate under strong disorder, particularly in the presence of spin-orbit coupling (SOC), is not fully understood. Here, we uncover a Z_2 topological bipolar skin effect in a non-Hermitian Rashba chain, where spin-up and spin-down eigenstates localize at opposite boundaries. By strictly computing the Lyapunov exponents and introducing a biorthogonal spin-separation index, we map the global phase diagram and reveal a hierarchical breakdown of topology. We demonstrate that the Z_2 skin effect is protected against moderate disorder but collapses into a trivial skin phase before the ultimate onset of Anderson localization. Our results establish a distinct regime of disorder-robust topological non-reciprocity, distinguishable from both the trivial bulk limit and the Anderson localized phase.

cond-mat.dis-nn↗

arXiv2025

Robust Universality of Non-Hermitian Anderson Transitions: From Dyson Singularity to Model-Independent Scaling

We investigate the universality of Anderson localization transitions in one-dimensional non-Hermitian systems exhibiting the skin effect. By developing a numerically stable Log-Space Non-Hermitian Scaling (LNS) method, we overcome the severe floating-point overflow issues associated with the exponential growth of transmittance (T ~ exp(2 gamma L)), enabling precision finite-size scaling analysis up to system sizes of L = 1200. We probe the critical behavior across three distinct disorder landscapes: uniform diagonal, binary diagonal, and off-diagonal (random hopping) disorder. While the uniform model exhibits a standard mobility edge, the off-diagonal model reveals a Dyson-like singularity at the band center (E = 0), where the system resists localization even at strong disorder due to sublattice symmetry protection. However, upon symmetry breaking (E != 0), we demonstrate that all considered models, regardless of the disorder distribution (continuous vs. discrete) or Hamiltonian structure (site vs. bond randomness), belong to the same robust universality class. The critical exponents are determined as nu = 1.50 +/- 0.00 and beta ~ 0.65 through unambiguous data collapse, establishing a model-independent description of non-Hermitian localization transitions.

cond-mat.stat-mech↗

arXiv2025

Universal Critical Scaling and Phase Diagram of the Non-Hermitian Skin Effect under Disorder

Standard scaling theory dictates that disorder leads to immediate localization in one-dimensional Hermitian systems. We demonstrate that non-Hermitian topology fundamentally alters this paradigm, protecting transport up to a substantial critical disorder strength. By employing a numerically stable log-space transfer matrix approach up to thermodynamic scales (N=1000), we identify a sharp phase transition from the topological skin phase to the Anderson localized phase. Finite-size scaling analysis reveals that this transition belongs to a unique universality class with critical exponents \nu\approx1.50 and \beta\approx0.65. Furthermore, we map the global phase diagram, confirming that the critical disorder scales as W_c\propto\sqrt\gamma, consistent with localization suppression by an imaginary vector potential. Our results establish the rigorous limits of non-Hermitian topological protection in imperfect media.

cond-mat.dis-nn↗