arXiv subjects

Soumya Ranjan Padhi

Publications and source records attributed to Soumya Ranjan Padhi.

9 recordsLinked to original sources

arXiv2026

Coupling induced emergent topology in a two-leg fermionic ladder

We investigate the ground state properties of spinless fermions on a two leg ladder, by allowing the nearest-neighbour hopping dimerization in one leg and uniform hopping in the other. In the non-interacting limit, we find that, at half-filling, the system exhibits robust topological behavior if the inter-leg hopping is allowed. Though depending on the dimerization pattern, the dimerized leg can be either topological or trivial in nature, here we show that by connecting such a leg to a uniform leg through inter-chain coupling, the overall system becomes topological irrespective of the dimerization pattern in the dimerized leg. As a result, a topological phase transition occurs as a function of the inter-leg hopping. When the inter-leg interaction is turned on, the topological phase survives, and we obtain an interaction induced topological phase transition. Finally, we reveal that when uniform interactions are included on all the bonds of the ladder, the topological phase transitions to a symmetry-broken charge-density wave (CDW) phase.

cond-mat.quant-gas↗

arXiv2026

Emergence of charge and spin current in non-Hermitian quantum ring

We investigate the charge and spin transport in a non-Hermitian ring of electrons subject to an external Zeeman field. By introducing non-Hermiticity through anti-Hermitian hopping in the nearest neighbour bonds, we demonstrate that anti-Hermiticity, along with the applied Zeeman field significantly modify the energy spectrum and strongly influence transport properties. As a result, we obtain that when antiferromagnetic Zeeman field is considered, a finite charge current emerges in both the real and imaginary parts of the current, which are in contrast to the ferromagnetic case where only the imaginary current exist. On the other hand, in both cases, the spin current vanishes. Interestingly, we reveal an emergence and strong enhancement of spin currents under balanced spin population upon introducing quasiperiodicity in the presence of antiferromagnetic ordering. At the same time, the charge current also exhibits substantial enhancement due to quasiperiodic modulation. These results highlight non-Hermitian quantum rings as versatile platforms for unconventional spin-charge transport.

cond-mat.mes-hall↗

arXiv2026

Spin-aligned butterfly spectral map in Non-Hermitian quasicrystals

The Non-Hermitian spinful Aubry-André-Harper (AAH) model in the presence of Rashba-type spin-orbit coupling (RSOC) and a spatially varying textured magnetic field is studied. Interestingly, our analysis produces a butterfly spectral map due to the non-trivial extent of localization of the states in the spectrum. This spectral map also exhibits an asymmetric spin alignment with respect to the wings of the butterfly. Our analysis also suggests that the onset of such a spectral map is a combined effect of the non-hermiticity, spin-orbit interaction, and the textured magnetic field.

cond-mat.dis-nn↗

arXiv2025

Non-Hermitian comb effect in coupled clean and quasiperiodic chains

We study localization properties in a system of non-Hermitian quasiperiodic chain coupled to a uniform chain or clean chain by inter-chain hopping. We find that in the limit of weak inter-chain coupling, such a coupled system exhibits transitions from delocalized to intermediate phase with increase in the non-Hermiticity parameter. However, for stronger inter-chain coupling strengths, the delocalized phase undergoes a transition to localized phase and then to an intermediate phase. Interestingly, the intermediate phase in this case exhibits the non-Hermitian comb effect (NHCE), i.e., the coexistence of localized and extended states rather than being well separated from each other by any mobility edge which is conventional in any intermediate phase. We further show that such a NHCE originates from the isolated site limit of the quasiperiodic chain and provide an analytical explanation supporting the numerical signatures.

cond-mat.quant-gas↗

arXiv2025

Flux-driven charge and spin transport in a dimerized Hubbard ring with Fibonacci modulation

We study quantum transport in a one-dimensional Hubbard ring with dimerized nearest-neighbor hoppings and a Fibonacci-modulated onsite potential. For non-interacting case our analysis reveals that at half-filling, the charge current along with the Drude weight decreases with increasing onsite potential when inter-cell hopping dominates over the intra-cell hopping, while for dominating intra-cell hopping it shows non-monotonic behavior with sharp peak at certain critical modulation strength, indicating enhanced transport. Moving away from half-filling gives rise to re-entrant features in both quantities at fillings associated with Fibonacci numbers. On the other hand, in spin-imbalanced systems, both spin and charge current shows multiple peaks and re-entrant behavior, tunable via hopping dimerization and filling. Including the on-site Hubbard interaction preserves the re-entrant behavior in current and moreover favors finite transport which is absent in the non-interacting ring. These results reveal rich interplay among Fibonacci modulated potential, electron fillings, hopping dimerization and interaction.

cond-mat.other↗

arXiv2025

Emergence of distinct exact mobility edges in a quasiperiodic chain

Mobility edges (MEs) constitute the energies separating the localized states from the extended ones in disordered systems. Going beyond this conventional definition, recent proposal suggests for an ME which separates the localized and multifractal states in certain quasiperiodic systems - dubbed as the anomalous mobility edges (AMEs). In this study, we propose an exactly solvable quasiperiodic system that hosts both the conventional and anomalous mobility edges under proper conditions. We show that with increase in quasiperiodic disorder strength, the system first undergoes a delocalization to localization transition through an ME of conventional type. Surprisingly, with further increase in disorder, we obtain that a major fraction of the localized states at the middle of the spectrum turn multifractal in nature. Such unconventional behavior in the spectrum results in two AMEs, which continue to exist even for stronger quasiperiodic disorder. We numerically obtain the signatures of the coexisting MEs complement it through analytical derivation using Avila's global theory. In the end we provide important signatures from the wavepacket dynamics.

cond-mat.quant-gas↗

arXiv2024

Anomalous spectrum in a non-Hermitian quasiperiodic chain

The spectra of particles in disordered lattices can either be completely extended or localized or can be intermediate which hosts both the localized and extended states separated from each other. In this work, however, we show that in the case of a one dimensional lattice with long-range hopping and non-Hermitian quasiperiodic onsite potential, the localized and extended states in the spectrum are intermixed with each other rather than well separated. As a result, an atypical intermediate phase appears where consecutive pairs of extended states intermittently appear in the pool of localized states. We also argue that such anomalous spectral intermixing can be realized in the short-range hopping limit by appropriate engineering of the onsite potential. Moreover, we obtain that the nature of the spectrum also reveals non-standard scenarios in the complex energy plane where the complex energies encircle real ones. These findings shed light on the intricate interplay between the non-Hermiticity and quasiperiodic disorder in the system.

cond-mat.dis-nn↗

arXiv2024

Quasiperiodic and periodic extended Hatano-Nelson model: Anomalous complex-real transition and non-Hermitian skin effect

We study the effect of quasiperiodic and periodic onsite potentials in a Hatano-Nelson model with next-nearest-neighbour hopping. By considering a non-reciprocal next-nearest-neighbour hopping and a quasiperiodic onsite potential under periodic boundary conditions, we show a breakdown of the typical correspondence between the delocalization-localization and complex-real transitions as a function of the potential strength. Moreover, we reveal that in the delocalized regime, when the potential strength increases, the eigenstates under open boundary conditions exhibit a bidirectional non-Hermitian skin effect, i.e., they tend to localize on both the edges instead of localizing on either of the edges. However, when a periodic onsite potential is considered, the system not only exhibits a bidirectional skin effect but also shows a complete direction reversal of the skin effect as a function of the onsite periodic potential.

cond-mat.quant-gas↗

arXiv2023

Re-entrant topological phase transition in a non-Hermitian quasiperiodic lattice

We predict a re-entrant topological transition in a one dimensional non-Hermitian quasiperiodic lattice. By considering a non-Hermitian generalized Aubry-André-Harper (AAH) model with quasiperiodic potential, we show that the system first undergoes a transition from the delocalized phase to the localized phase and then to the delocalized phase as a function of the hermiticity breaking parameter. This re-entrant delocalization-localization-delocalization transition in turn results in a re-entrant topological transition identified by associating the phases with spectral winding numbers. Moreover, we find that these two transitions occur through intermediate phases hosting both extended and localized states having real and imaginary energies, respectively. We find that these phases also possess non-trivial winding numbers which are different from that of the localized phase.

cond-mat.quant-gas↗