arXiv subjects

Adipta Pal

Publications and source records attributed to Adipta Pal.

8 recordsLinked to original sources

arXiv2026

Transition between one- and two-dimensional topology in a Chern insulator of finite width

Topology in quantum systems is typically considered in infinite crystals in one, two, or higher integer dimensions. Here, we show that one can continuously transform a system between a topological phase associated with one dimension and a topological phase associated with two dimensions without closing the energy gap. In this process, the dimension of the system itself changes. Concretely, we investigate a modified version of the Qi-Wu-Zhang model and develop a procedure to smoothly shrink the width of the system in one direction. By tracking gaps which remain open throughout the modulation, we establish a smooth transition from a two-dimensional to a one-dimensional topological insulator. In between the system exhibits both one- and two-dimensional topology, and the way the system accomplishes the transition is by making the one-dimensional topology more robust as the width decreases, while the two-dimensional topology becomes less robust. Finally, we show how the gaps arise from hybridization of edge states due to the finite width.

cond-mat.mes-hall↗

arXiv2024

Signatures of the quantum skyrmion Hall effect in the Bernevig-Hughes-Zhang model

Given recent discovery of the quantum skyrmion Hall effect, we re-examine the related canonical Bernevig-Hughes-Zhang (BHZ) model for the quantum spin Hall insulator. Within the framework of the quantum skyrmion Hall effect, isospin degree(s) of freedom of the BHZ model encode additional spatial dimensions. Consistent with this framework, we observe phenomena similar to those of the four dimensional Chern insulator, revealed by weakly breaking time-reversal symmetry. Bulk-boundary correspondence of these states includes real-space boundary orbital angular momentum textures and gapless boundary modes that are robust against magnetic disorder, consistent with compactified three dimensional boundary Weyl nodes (WN$_F$s) of the quantum skyrmion Hall effect. These theoretical findings are furthermore consistent with past experimental work reporting unexpected edge conduction in HgTe quantum wells under applied Zeeman and orbital magnetic fields. This past work is therefore potentially the first known experimental observation of signatures of the quantum skyrmion Hall effect beyond the quantum Hall effect.

cond-mat.mes-hall↗

arXiv2024

Finite-size topological phases from semimetals

Topological semimetals are some of the topological phases of matter most intensely-studied experimentally. The Weyl semimetal phase, in particular, has garned tremendous, sustained interest given fascinating signatures such as the Fermi arc surface states and the chiral anomaly, as well as the minimal requirements to protect this three-dimensional topological phase. Here, we show that thin films of Weyl semimetals (which we call quasi-(3-1)-dimensional, or q(3-1)d) generically realize finite-size topological phases distinct from 3d and 2d topological phases of established classification schemes: response signatures of the 3d bulk topology co-exist with topologically-protected, quasi-(3-2)d Fermi arc states or chiral boundary modes due to a second, previously-unidentified bulk-boundary correspondence. We show these finite-size topological semimetal phases are realized by Hamiltonians capturing the Fermiology of few-layer Van der Waals material MoTe2 in experiment. Given the broad experimental interest in few-layer Van der Waals materials and topological semimetals, our work paves the way for extensive future theoretical and experimental characterization of finite-size topological phases.

cond-mat.mes-hall↗

arXiv2023

Robust quantisation of circular photogalvanic effect in multiplicative topological semimetals

Nonlinear response signatures are increasingly recognized as useful probes of condensed matter systems, in particular for characterisation of topologically non-trivial states. The circular photogalvanic effect (CPGE) is particularly useful in study of topological semimetals, as the CPGE tensor quantises for well-isolated topological degeneracies in strictly linearly-dispersing band structures. Here, we study multiplicative Weyl semimetal band-structures, and find that the multiplicative structure robustly protects the quantization of the CPGE even in the case of non-linear dispersion. Computing phase diagrams as a function of Weyl node tilting, we find a variety of quantised values for the CPGE tensor, revealing that the CPGE is also a useful tool in detecting and characterising parent topology of multiplicative topological states.

cond-mat.mes-hall↗

arXiv2023

Multiplicative Majorana zero-modes

Topological qubits composed of unpaired Majorana zero-modes are under intense experimental and theoretical scrutiny in efforts to realize practical quantum computation schemes. In this work, we show the minimum four \textit{unpaired} Majorana zero-modes required for a topological qubit according to braiding schemes and control of entanglement for gate operations are inherent to multiplicative topological phases, which realize symmetry-protected tensor products -- and maximally-entangled Bell states -- of unpaired Majorana zero-modes known as multiplicative Majorana zero-modes. We introduce multiplicative Majorana zero-modes as topologically-protected boundary states of both one and two-dimensional multiplicative topological phases, using methods reliant on multiplicative topology to construct relevant Hamiltonians from the Kitaev chain model. We furthermore characterize topology in the bulk and on the boundary with established methods while also introducing techniques to overcome challenges in characterizing multiplicative topology. In the process, we explore the potential of these multiplicative topological phases for an alternative to braiding-based topological quantum computation schemes, in which gate operations are performed through topological phase transitions.

quant-ph↗

arXiv2023

Multiplicative topological semimetals

Exhaustive study of topological semimetal phases of matter in equilibriated electonic systems and myriad extensions has built upon the foundations laid by earlier introduction and study of the Weyl semimetal, with broad applications in topologically-protected quantum computing, spintronics, and optical devices. We extend recent introduction of multiplicative topological phases to find previously-overlooked topological semimetal phases of electronic systems in equilibrium, with minimal symmetry-protection. We show these multiplicative topological semimetal phases exhibit rich and distinctive bulk-boundary correspondence and response signatures that greatly expand understanding of consequences of topology in condensed matter settings, such as the limits on Fermi arc connectivity and structure, and transport signatures such as the chiral anomaly. Our work therefore lays the foundation for extensive future study of multiplicative topological semimetal phases.

cond-mat.mes-hall↗

arXiv2019

Quadrature operator eigenstates and wavefunctions of $f$-deformed oscillators

This paper is dedicated to finding the quadrature operator eigenstates and wavefunctions of the most general $f$-deformed oscillators. A definition for quadrature operator for deformed algebra is derived to obtain the quadrature operator eigenstates. A new set of polynomials are obtained using this quadrature operator and these polynomials are used to find explicitly the wavefunctions of the deformed oscillators. We have plotted wavefunctions for three different types of deformations and compared it with the wavefunctions of the non-deformed oscillator. Our result will immensely help the research groups working in the quantum state reconstruction and quantum information theory of deformed states.

quant-ph↗

arXiv2018

PT-Symmetry and Supersymmetry: Interconnection of Broken and Unbroken Phases

The broken and unbroken phases of PT and supersymmetry in optical systems are explored for a complex refractive index profile in the form of a Scarf potential, under the framework of supersymmetric quantum mechanics. The transition from unbroken to the broken phases of PT-symmetry, with the merger of eigenfunctions near the exceptional point is found to arise from two distinct realizations of the potential, originating from the underlying supersymmetry. Interestingly, in PT-symmetric phase, spontaneous breaking of supersymmetry occurs in a parametric domain, possessing non-trivial shape invariances, under reparametrization to yield the corresponding energy spectra. One also observes a parametric bifurcation behaviour in this domain. Unlike the real Scarf potential, in PT-symmetric phase, a connection between complex isospectral superpotentials and modified KdV equation occurs, only with certain restrictive parametric conditions. In the broken PT-symmetry phase, supersymmetry is found to be intact in the entire parameter domain yielding the complex energy spectra, with zero-width resonance occurring at integral values of a potential parameter.

quant-ph↗