Quantum Transport Patterns Revealed in Helical Lattice Structures Through Localization and Current Analysis

Localization Dynamics in Quantum Systems

Recent research published in Scientific Reports has uncovered detailed patterns of electron localization and persistent currents in quasiperiodic disordered helical lattices. According to the report, these many-body currents quantify how the filled Fermi sea responds to variations in magnetic fluxes, providing complementary transport diagnostics alongside single-particle localization measures. The study reportedly examines how hopping anisotropy, disorder strength, and applied magnetic flux interact across conducting and insulating regimes.

Localization Dynamics in Quantum Systems
Mapping Localization Transitions
Mesoscopic Scale Effects
Persistent Current Behavior
Localization Thresholds and Current Quenching

Mapping Localization Transitions

Sources indicate the research team employed a composite metric to classify localization states across the lattice system. Analysis reportedly shows red regions in localization maps correspond to homogeneous regimes where spectra are either fully extended or localized, while bluish regions represent mixed states where both localized and extended states coexist. The report states that as inter-ring hopping increases, the mixed region shifts to higher values of potential strength, with larger inter-ring hopping broadening and hybridizing minibands.

Researchers suggest this breaks Aubry-André self-duality and generates mobility edges, where flatter subbands localize near the AA-like threshold while more dispersive states remain extended. The mixed region reportedly broadens with hopping strength and starts vanishing when coupling becomes strong enough to localize all subbands. Analysts note that stronger coupling between rings increases lattice connectivity, making it harder for disorder to localize wave functions.

Mesoscopic Scale Effects

The study focuses on mesoscopic-scale systems, particularly 400-site lattices, which sources describe as optimal for observing clear localization transitions while maintaining measurable nondecaying current oscillations. According to reports, larger lattices would suppress oscillation amplitudes below detectable levels, masking the mesoscopic transport phenomena under investigation. The research team reportedly found that at mesoscopic scales, the composite metric can become numerically unstable, prompting them to track individual localization measures separately for more reliable analysis.

Analysis suggests magnetic fluxes significantly impact localization in extended regimes, where destructive interference localizes states when fluxes reach half or full quantum values. However, in localized regimes where potential strength exceeds critical thresholds, magnetic flux reportedly has negligible effect, indicating that flux tuning can localize states in delocalized regimes but cannot reverse insulating conditions.

Persistent Current Behavior

The research examines equilibrium persistent currents in rotated ring helices, computing toroidal and poloidal currents as derivatives of the ground-state energy with respect to dimensionless fluxes. At weak potential strength, both current types reportedly exhibit large, multi-harmonic oscillations characteristic of metallic regimes with multiple conducting channels. As potential strength increases, localization length decreases exponentially, suppressing higher harmonics and transforming multi-harmonic oscillations into nearly sinusoidal patterns.

According to the analysis, current amplitudes show non-monotonic dependence on quasiperiodic potential strength. In disorder-free helical lattices, single-particle bands are perfectly sinusoidal and symmetric, but small potential modulation perturbs canceling states and enhances persistent currents. Further increasing potential strength shrinks localization length, filters high-order harmonics, and suppresses current amplitudes to nearly sinusoidal traces of small magnitude.

Localization Thresholds and Current Quenching

The report indicates that persistent currents vanish when the system enters a localized insulating regime, correlating with mixed-to-localized crossovers observed in localization measures. Researchers note that localization of the many-body ground state occurs when single-particle states below the Fermi level cross into the localized region. Analysis suggests the point where current becomes flux-insensitive represents the largest critical value across the occupied window, with this threshold shifting depending on Fermi energy position relative to band edges.

At half-filling, the study reportedly shows occupied states localize around specific potential strength values, even though unoccupied high-energy bands remain extended to higher strengths. Localization length analysis supports this finding, showing extracted lengths collapse and cross thresholds at specific values, causing current harmonics to suppress and persistent currents to vanish.

OPTIONAL REFERENCE LINKS:
Mesoscopic Physics
Magnetic Flux

References

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