arXiv subjects

Tapan Mishra

Publications and source records attributed to Tapan Mishra.

At least 19 recordsLinked to original sources

arXiv2026

Quantum computer-based simulation of Stark many-body localization in a 1D Fermi-Hubbard model

Many-body localization (MBL) is a dynamical phenomenon that describes the non-ergodicity of isolated quantum many-body systems. In contrast to thermalization, this phenomenon leads to a long-lived memory of initial states of local systems and slow growth of entanglement. In this work, we study Stark MBL in a 12-qubit correlated fermionic system described by the one-dimensional Fermi-Hubbard model using Hamiltonian simulation on an IBM superconducting qubit quantum computer. To enable such a computation on current-day noisy hardware, we combine a series of compilation steps, including the use of the spin-resolved Jordan-Wigner transformation, employing SWAP networks, and integrating a tensor-network-based quantum circuit optimization routine on top of a standard circuit optimization pipeline. As a result, there is approximately an 88$\%$ and 87$\%$ reduction in two-qubit gate count and circuit depth, respectively. Through such simulations of the real-time dynamics using Trotterized quantum circuits, we exhibit a crossover from thermalizing dynamics of the system at a weak tilt of the field to a strongly localized behavior at large tilt with short evolution times. We also benchmark our obtained results with respect to those from exact simulations.

quant-ph↗

arXiv2026

Engineering edge states in two-leg SSH ladder and their topoelectric circuit realization

We study the topological phase transition in a two-leg Su-Schrieffer-Heeger (SSH) ladder by redefining the unit-cell structure. For both identical hopping dimerization pattern (uniform) and alternate hopping dimerization pattern (staggered) along the legs of the ladder, we demonstrate that different unit-cell choices generate different topological phases and phase transitions. In the uniformly dimerized ladder, variation of the inter-leg coupling induces a transition from topological phase to another topological phase through a gapless region. In contrast, the staggered dimerization configuration exhibits a richer phase structure, supporting both topological-topological and trivial-topological transitions occurring through a single gap-closing point, depending on the unit-cell definition. The phases are characterized through bulk-boundary correspondence, edge-state analysis, and bulk topological invariants. Interestingly, we obtain that while all the topological phases host two zero energy edge states each, the topological phase for the staggerred dimerization case at small inter-leg coupling hosts four edge states. We then perform topoelectric circuit simulation and experiments to observe the signatures of the topological phases. By using circuit impedance and voltage responses we establish the emergence of distinct edge modes in the circuit. Our analysis provides a route to engineer topological edge modes in a two-leg SSH ladder set-up.

cond-mat.other↗

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

Majorana bound states in a hybrid Kitaev ladder with long-range pairing

We investigate an inter-leg coupled hybrid Kitaev ladder composed of two parallel superconducting chains with distinct pairing interactions. The upper chain of the ladder hosts conventional $p$-wave pairing, while the lower chain exhibits long-range pairing that decays algebraically with distance. We demonstrate that the mutual influence of long-range pairing exponent, chemical potential, and inter-leg coupling strength gives rise to a rich topological phase diagram characterized by multiple Majorana zero modes and massive Dirac modes. In particular, we show that the inter-leg coupling renormalizes the effective energy scales, leading to a systematic shift of the topological phase boundaries and enabling controlled tuning of the Majorana modes. Furthermore, we identify a transition from a two Majorana zero mode phase to a phase encapsulating four Majorana zero modes, as the long-range pairing exponent is varied. This transition is accompanied by a crossover regime in which Majorana zero modes coexist with massive Dirac modes, reflecting hybridization between edge and bulk excitations. This ladder thus provides a minimal and attractive platform for realizing the impact of a long-range pairing on topological phases. Our results highlight the potential of long-range hybrid systems for engineering tunable topological states relevant for quantum information applications.

quant-ph↗

arXiv2026

Emergence of a molecular quantum liquid in one dimension

We investigate the fate of a one-dimensional lattice superfluid formed by hard-core bosons, aka `atoms' (alternatively, a free spinless Fermi sea) subjected to nearest-neighbor attractive Hubbard-like interactions only in subgroups of two sites. The system, as expected, stabilizes a fluid of dimerized molecules at large attractive interactions. However, the composite molecules have an effective meek hopping scale and dominant repulsive interactions solely due to virtual quantum fluctuations. Interestingly, at an intermediate attractive potential, the system realizes a phase-separated region where the system is in an absorbing state. We show that this phase-separated region is due to an emergent attractive interaction between the dimers which leads to a local charge-density wave puddle where particles effectively cluster with local half-filling. Moreover the molecular superfluid gets spontaneously charge-ordered in the addition of an unpaired atom, reflecting the extreme sensitivity of the system to the existence of lone atoms. Using density-matrix renormalization group studies and effective low-energy Hamiltonians, we isolate the quantum processes to uncover the physics behind molecule formation in a strongly interacting one-dimensional system.

cond-mat.quant-gas↗

arXiv2026

Floquet-induced suppression of thermalization in a quasiperiodic Ising chain

Many-body localized (MBL) systems are known to thermalize in periodically driven systems. In this work, we demonstrate that under proper driving protocol, this thermalization this thermalization can be resisted such that the MBL phase turns into a non-ergodic extended phase, known as the many-body critical (MBC) phase. Considering a kicked quasiperiodic Ising chain, we show that while at high-frequency driving the ergodic, MBL, and the MBC phases coexist, at moderate driving frequencies the MBL phase is completely suppressed and the MBC phase proliferates in the parameter space. Using quasienergy statistics, Floquet eigenstates, autocorrelation dynamics, and entanglement growth, we characterize the emergent phases and identify non-monotonic signatures revealing richness of the nonergodic phases. Our results establish Floquet driving as a powerful route to stabilizing nonergodic extended many-body phases beyond the conventional Floquet-MBL paradigm.

cond-mat.dis-nn↗

arXiv2026

Tunable Floquet selection rules in a driven Ising chain

We study a periodically driven spin-$1/2$ Ising chain with a nearest-neighbour coupling and longitudinal field while a weak transverse field induces single-spin flips. Through Floquet perturbation theory (FPT), we obtain signatures of Hilbert space fragmentation (HSF) and an unconventional form of dynamical localisation which we call the Floquet freezing. Our analysis suggests that these observations emerge due to a single Floquet selection rule that dictates the prethermal dynamics. For a special value of the field-to-interaction strength ratio together with commensurate drive periods, this rule permits only a constrained subset of bulk spin flips, leading to prethermal HSF in the full spin-$1/2$ Hilbert space. Under open boundary conditions, the same rule suppresses boundary spin flips up to higher order in perturbation and produces long-lived prethermal edge memory, which is neither topological in origin nor is a strong zero mode. Furthermore, under periodic boundary conditions, the largest surviving fragment is exactly the PXP sector at leading order and therefore exhibits Floquet-inherited scar phenomenology in the prethermal window. At higher commensurate ratios of field strength to interaction strength, all first-order single-spin-flip channels are suppressed and the system enters a regime of Floquet freezing. Hence, our study leverages the selection rules obtained through Floquet perturbation theory to obtain exotic prethermal phenomena at different parameter regimes.

cond-mat.other↗

arXiv2026

Emergent criticality in the Aubry-André model with periodic modulation

The Aubry-André model describes a system with quasiperiodic lattice modulation. In one dimension the AAH model is known to exhibit a sharp metal to insulator transition at a self-dual critical point at which all the states in the spectrum are critical or multifractal in nature. While such criticality is immediately destroyed by an additional onsite periodic modulation, we show an emergent criticality in the limit of strong periodic modulation strength under proper conditions. The resulting strong-modulation critical phase exhibits multifractal eigenstates and singular continuous spectra, belonging to the universality class of the critical Harper model. Moreover, we reveal that additional periodic potential of period N in the quasiperiodic chain folds the spectrum into N bands with quasiperiodicity being enhanced by a factor of N, producing N numbers of Hofstadter butterflies in each band. Our results reveal a general mechanism for engineering robust criticality and spectral replication in quasiperiodic systems.

cond-mat.dis-nn↗

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

Multiple many-body localization transitions in a driven non-Hermitian quasiperiodic chain

We investigate the fate of a many-body localized phase in a non-Hermitian quasiperiodic model of hardcore bosons subjected to periodic driving. While in general, the many-body localized system is known to thermalize with increasing driving period due to Floquet heating, in this case, we demonstrate that the initially localized system first delocalizes and then localizes again, resulting in a re-entrant many-body localization (MBL) transition as a function of the driving period. Strikingly, further increase in the driving period results in a series of localization-delocalization transitions leaving behind traces of extended regimes (islands) in between MBL phases. Furthermore, non-Hermiticity renders the extended islands boundary-sensitive, resulting in a Floquet many-body skin effect under open boundaries. We present numerical evidence from spectral and dynamic studies, confirming these findings. Our study opens new pathways for understanding the interplay between non-Hermiticity and quasiperiodicity in driven systems.

cond-mat.dis-nn↗

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 non-trivial phases in interacting non-Hermitian quasiperiodic chains with power-law hopping

In the last few years, several works have identified the concurrence of the spectral, delocalization-localization and topological phase transitions in non-Hermitian quasiperiodic systems in the presence of time-reversal symmetry (TRS), with or without interaction. In this work, we investigate one-dimensional interacting non-Hermitian quasiperiodic lattices with asymmetric power-law hopping and unveil that although the Hamiltonian respects the TRS, the reality of the eigenspectrum does not necessarily indicate a topologically trivial non-Hermitian many-body localization (NHMBL) regime. In fact, we reveal the emergence of a topologically trivial intermediate regime, where the states that are primarily multifractal in nature can also possess a fully real spectrum, thereby restoring the TRS before crossing over to the NHMBL phase. Moreover, in the entire intermediate regime, the interaction completely destroys the multifractal and mobility edges observed in the non-interacting counterpart. Besides, we unveil that due to the long-range nature of the hopping, the entire topologically non-trivial ergodic regime under the periodic boundary condition does not always give rise to boundary localized skin modes under the open boundary condition. Our findings thus advances and deepens the understanding about the emergence of non-trivial phases due to the interplay of interaction and long-range hopping in non-Hermitian quasiperiodic systems.

cond-mat.dis-nn↗

arXiv2025

Topological phase transition through tunable nearest-neighbor interactions in a one-dimensional lattice

We investigate the phase diagram of a one-dimensional model of hardcore bosons or spinless fermions with tunable nearest-neighbor interactions. By introducing alternating repulsive and attractive interactions on consecutive bonds, we show that the system undergoes a transition from a bond-ordered (BO) phase to a charge-density wave-II (CDW-II) phase as the attractive interaction strength increases at a fixed repulsive interaction. For a specific interaction pattern, the BO phase exhibits topological properties, which vanish when the pattern is altered, leading to a transition from a topological BO phase to a trivial BO phase through a gap-closing point where both interactions vanish. We identify these phases using a combination of order parameters, topological invariants, edge-state analysis and Thouless charge pumping. By extending our analysis beyond half-filling, we explore the phase diagram across all densities and identify the superfluid (SF) and the pair-superfluid (PSF) phases, characterized by single-particle and bound-pair excitations at incommensurate densities. The proposed model is experimentally realizable in platforms such as Rydberg excited or ultracold atoms in optical lattices, offering a versatile framework to study such interplay between topology and interactions in low-dimensional systems.

cond-mat.quant-gas↗

arXiv2025

Reentrant topology and reverse pumping in a quasiperiodic flux ladder

Topological phases of matter are known to be unstable against strong onsite disorder in one dimension. In this work, however, we propose that in the case of a topological ladder, an onsite quasiperiodic disorder under proper conditions, first destroys the initial topological phase and subsequently, induces another topological phase through a gap-closing point. Remarkably, by allowing a staggered flux piercing through the plaquettes of the ladder, the gapless point bifurcates into two gapless critical lines, resulting in a trivial gapped phase sandwiched between the two topological phases. This results in a scenario where the system first undergoes a transition from one topological phase to a trivial phase and then to the other topological phase as a function of the quasiperiodic disorder strength. Such disorder induced re-entrant topological phase transition reveals a phenomenon of direction reversal in the topological transport, which we identify through Thouless charge pumping.

cond-mat.quant-gas↗

arXiv2025

Anomalous slow-down of the bound state dynamics in a non-locally coupled quantum circuit

Additional hopping channels in a tight-binding lattice is known to introduce faster dynamics of a quantum mechanical particle. However, we show that in the case of a repulsively bound state, the dynamics becomes abnormally slow when next-nearest neighbor (NNN) hopping is allowed for the particles. We show that such slowing down occurs for some magic strength of the NNN hopping at which the bound state band exhibits a quasi-flatband feature. We reveal this anomalous dynamical behavior by analyzing the quench dynamics of two nearest neighbor (NN) spin excitations (magnons) on a ferromagnetic chain by allowing both NN and NNN couplings. By implementing digital quantum computing simulations on a NISQ device, we obtain such non-trivial signatures and complement the results with exact numerical calculations. Moreover, through perturbative arguments, we reveal that the slowing down is due to the destructive interference between different paths associated to the bound state dynamics.

cond-mat.quant-gas↗

arXiv2025

Realizing non-trivial doublon formation using a quantum computer

Dynamical formation of doublons or onsite repulsively bound pairs of particles on a lattice is a highly non-trivial phenomenon. In this work, we show the signatures of doublon formation in a quantum computer by simulating the continuous time quantum walk in the framework of the one dimensional extended Fermi-Hubbard model. By considering two up-component and one down-component particles initially created at the three neighbouring sites at the middle of the lattice and allowing intra- (inter-) component nearest neighbour (onsite) interactions we show the formation a stable onsite doublon in the quantum walk. The probability of such doublon formation is more (less) if the hopping strength of the down particle is weaker (stronger) compared to the up particle. On the contrary, for an initial doublon along with a free up particle, the stability of the doublon is more prominent than the doublon dissociation in the dynamics irrespective of the hopping asymmetry between the two components. We first numerically obtain the signatures of the stable doublon formation in the dynamics and then observe them using Noisy Intermediate-Scale Quantum (NISQ) devices.

quant-ph↗