Showing 1–12 of 12 results for author: Batra, N

Three-dimensional Foliated Fractional Quantum Hall Phases

Authors: Sahana Das, Navketan Batra, Andrea Kouta Dagnino, Dan Mao, Nicolas Regnault, Glenn Wagner, Titus Neupert

Abstract: Foliated topological orders in three dimensions are layered systems in which anyons are free to move within a layer but cannot hop between them. A simple model with such a phase is a stack of decoupled two-dimensional electron gases in a strong magnetic field, each in the same fractional quantum Hall state. By focusing on the case of filling $ν=1/3$ of the lowest Landau level in each layer, we sho… ▽ More Foliated topological orders in three dimensions are layered systems in which anyons are free to move within a layer but cannot hop between them. A simple model with such a phase is a stack of decoupled two-dimensional electron gases in a strong magnetic field, each in the same fractional quantum Hall state. By focusing on the case of filling $ν=1/3$ of the lowest Landau level in each layer, we show that (i) the limit of decoupled Laughlin states is stable upon introducing interlayer interactions and (ii) the system can enter a spontaneously layer-trimerized foliated non-Abelian Fibonacci phase. We support our claims by numerical exact diagonalization of up to 10 layers as well as perturbative analytical calculations. Specifically, we show that the foliated Fibonacci phase exists in the 9-layer system with pseudopotential interactions within and between neighboring layers. We identify the phase via quasihole counting and by calculating the overlap with a model wave function which we derive from the associated conformal field theory. Our numerical results suggest the possibility of realizing these phases in layered van der Waals crystals in strong magnetic fields, as well as in multilayer heterostructures. △ Less

Submitted 17 June, 2026; originally announced June 2026.

Anyonic analogue of optical Mach-Zehnder interferometer

Authors: Navketan Batra, Zezhu Wei, Smitha Vishveshwara, D. E. Feldman

Abstract: Anyonic interferometry is a direct probe of fractional statistics. We propose an interferometry geometry that parallels an optical Mach-Zehnder interferometer and offers several advantages over existing interferometry schemes. In contrast to the currently studied electronic Mach-Zehnder interferometer, our setup has no drain inside the device so that the trapped topological charge is time-independ… ▽ More Anyonic interferometry is a direct probe of fractional statistics. We propose an interferometry geometry that parallels an optical Mach-Zehnder interferometer and offers several advantages over existing interferometry schemes. In contrast to the currently studied electronic Mach-Zehnder interferometer, our setup has no drain inside the device so that the trapped topological charge is time-independent. In contrast to electronic Fabry-Pérot interferometry, anyons cannot go around the device more than once. Thus, the interference signal has a straightforward interpretation in terms of anyonic statistical phases. The proposed geometry suppresses the undesirable effects of bulk-edge coupling. Moreover, the setup allows for simple exact solutions for the electric current and noise for an arbitrary quasiparticle tunneling strength in a broad range of conditions. The structure of the solutions is similar to that for non-interacting electrons but reflects fractional charge and statistics. We present results for electric current and noise in Jain states and address thermal interferometry at zero voltage bias. △ Less

Submitted 22 September, 2025; v1 submitted 18 July, 2025; originally announced July 2025.

Comments: 25 pages, 8 figures, accepted for publication in PRB

Journal ref: Phys. Rev. B 112, 125305 (2025)

Excitons in the Fractional Quantum Hall Effect

Authors: Naiyuan J. Zhang, Ron Q. Nguyen, Navketan Batra, Xiaoxue Liu, Kenji Watanabe, Takashi Taniguchi, D. E. Feldman, J. I. A. Li

Abstract: Excitons, Coulomb-driven bound states of electrons and holes, are typically composed of integer charges. However, in bilayer systems influenced by charge fractionalization, a more exotic form of interlayer exciton can emerge, where pairing occurs between constituents that carry fractional charges. Despite numerous theoretical predictions for such fractional excitons, their experimental observation… ▽ More Excitons, Coulomb-driven bound states of electrons and holes, are typically composed of integer charges. However, in bilayer systems influenced by charge fractionalization, a more exotic form of interlayer exciton can emerge, where pairing occurs between constituents that carry fractional charges. Despite numerous theoretical predictions for such fractional excitons, their experimental observation has remained elusive. Here, we report transport signatures of excitonic pairing within fractional quantum Hall effect states. By probing the composition of these excitons and their impact on the underlying wavefunction, we uncover two novel quantum phases of matter. One of these orders can be viewed as the fractional counterpart of the exciton condensate at a total filling of one, while the other involves a more unusual type of exciton that obeys fermionic and anyonic quantum statistics, challenging the standard paradigm of bosonic excitons. △ Less

Submitted 20 September, 2024; v1 submitted 25 July, 2024; originally announced July 2024.

Comments: 9 pages for main text with 4 figures. In total of 24 pages and 15 figures

A Bound on Topological Gap from Newton's Laws

Authors: Navketan Batra, D. E. Feldman

Abstract: A striking general bound on the energy gap in topological matter was recently discovered in Ref. [Onishi and Fu, Phys. Rev. X {\bf 14}, 011052 (2024)]. A non-trivial indirect derivation builds on the properties of optical conductivity at an arbitrary frequency. We propose a simpler derivation, allowing multiple generalizations, such as a universal bound on a gap in anisotropic systems, systems wit… ▽ More A striking general bound on the energy gap in topological matter was recently discovered in Ref. [Onishi and Fu, Phys. Rev. X {\bf 14}, 011052 (2024)]. A non-trivial indirect derivation builds on the properties of optical conductivity at an arbitrary frequency. We propose a simpler derivation, allowing multiple generalizations, such as a universal bound on a gap in anisotropic systems, systems with multiple charge carrier types, and topological systems with zero Hall conductance. The derivation builds on the observation that the bound equals $\hbar$ times the ratio of the force by the external electric field on the charge carriers and their total kinematic momentum in the direction perpendicular to the force. △ Less

Submitted 4 December, 2024; v1 submitted 24 July, 2024; originally announced July 2024.

Comments: 5 pages

Journal ref: Phys. Rev. B 110, 235133 (2024)

Anyonic Mach-Zehnder interferometer on a single edge of a 2D electron gas

Authors: Navketan Batra, Zezhu Wei, Smitha Vishveshwara, D. E. Feldman

Abstract: Anyonic Fabry-Pérot and Mach-Zehnder interferometers have been proposed theoretically and implemented experimentally as tools to probe electric charges and statistics of anyons. The experimentally observed visibility of Aharonov-Bohm oscillations is maximal at a high transmission through an interferometer but simple theoretical expressions for the electric currents and noises are only available at… ▽ More Anyonic Fabry-Pérot and Mach-Zehnder interferometers have been proposed theoretically and implemented experimentally as tools to probe electric charges and statistics of anyons. The experimentally observed visibility of Aharonov-Bohm oscillations is maximal at a high transmission through an interferometer but simple theoretical expressions for the electric currents and noises are only available at low visibility. We consider an alternative version of a Mach-Zehnder interferometer, in which anyons tunnel between co-propagating chiral channels on the edges of quantum Hall liquids at the filling factors $n/(2n+1)$. We find simple exact solutions for any transmission. The solutions allow a straight-forward interpretation in terms of fractional charges and statistics. △ Less

Submitted 9 August, 2023; originally announced August 2023.

Comments: 6 pages, 2 figures

Journal ref: Phys. Rev. B 108, L241302 (2023)

Different fractional charges from auto- and cross-correlation noise in quantum Hall states without upstream modes

Authors: Navketan Batra, D. E. Feldman

Abstract: Fractional charges of anyons can be extracted from shot noise in two ways. One can use either the auto-correlation noise of the current in one drain or the cross-correlation noise between two drains on the two sides of the device. The former approach typically overestimates the charge. This may happen due to upstream edge modes. We propose a mechanism for the excess auto-correlation noise without… ▽ More Fractional charges of anyons can be extracted from shot noise in two ways. One can use either the auto-correlation noise of the current in one drain or the cross-correlation noise between two drains on the two sides of the device. The former approach typically overestimates the charge. This may happen due to upstream edge modes. We propose a mechanism for the excess auto-correlation noise without upstream modes. It applies to systems with multiple co-propagating edge modes and assumes that the noise is measured at a low but non-zero frequency. △ Less

Submitted 7 May, 2024; v1 submitted 7 July, 2023; originally announced July 2023.

Comments: 6 pages, 2 figures. Accepted for publication in Physical Review Letters

Journal ref: Phys. Rev. Lett. 132, 226601 (2024)

Thermal interferometry of anyons

Authors: Zezhu Wei, Navketan Batra, V. F. Mitrović, D. E. Feldman

Abstract: Anyonic interferometry probes the braiding phases of excitations in topologically ordered matter. This technique is well established for charged quasiparticles in the fractional quantum Hall effect. We propose to extend it to neutral anyons, such as Ising anyons in Kitaev magnets and quasiparticles in other neutral spin liquids. We find that the thermal current through an interferometer is sensiti… ▽ More Anyonic interferometry probes the braiding phases of excitations in topologically ordered matter. This technique is well established for charged quasiparticles in the fractional quantum Hall effect. We propose to extend it to neutral anyons, such as Ising anyons in Kitaev magnets and quasiparticles in other neutral spin liquids. We find that the thermal current through an interferometer is sensitive to the statistics of tunneling quasiparticles. We present a systematic investigation of signatures of various Abelian and non-Abelian topological orders in Fabry-Pérot and Mach-Zehnder interferometers. The heat current through a Fabry-Pérot device is different for different topological orders and depends on the topological charge inside the interferometer. A Mach-Zehnder device shows interference in topologically trivial systems only. For a non-trivial statistics, the heat current reduces to the sum of the contributions from two constrictions in the interferometer. Furthermore, we identify another probe of topological order that involves the scaling of the thermal current through a single tunneling contact at low temperatures. The current shows a universal temperature dependence, sensitive to the topological order in the system. △ Less

Submitted 1 March, 2023; v1 submitted 13 September, 2022; originally announced September 2022.

Comments: 36 pages, 13 figures, 1 table, accepted for publication in PRB

Journal ref: Phys. Rev. B 107, 104406 (2023)

Pairing symmetries in the Zeeman-coupled extended attractive Hubbard model

Authors: Swagatam Nayak, Navketan Batra, Sanjeev Kumar

Abstract: By introducing the possibility of equal- and opposite-spin pairings concurrently, we show that the extended attractive Hubbard model (EAHM) exhibits rich ground state phase diagrams with a variety of singlet, triplet, and mixed parity superconducting orders. We study the competition between these superconducting pairing symmetries invoking an unrestricted Hartree-Fock- Bogoliubov-de Gennes (HFBdG)… ▽ More By introducing the possibility of equal- and opposite-spin pairings concurrently, we show that the extended attractive Hubbard model (EAHM) exhibits rich ground state phase diagrams with a variety of singlet, triplet, and mixed parity superconducting orders. We study the competition between these superconducting pairing symmetries invoking an unrestricted Hartree-Fock- Bogoliubov-de Gennes (HFBdG) mean-field approach, and we use the d-vector formalism to characterize the nature of the stabilized superconducting orders. We discover that, while all other types of orders are suppressed, a non-unitary triplet order dominates the phase space in the presence of an in-plane external magnetic field. We also find a transition between a non-unitary to unitary superconducting phase driven by the change in average electron density. Our results serve as a reference for identifying and understanding the nature of superconductivity based on the symmetries of the pairing correlations. The results further highlight that EAHM is a suitable effective model for describing most of the pairing symmetries discovered in different materials. △ Less

Submitted 13 July, 2021; originally announced July 2021.

Journal ref: Scientific Reports 11, 22724 (2021)

Current-Induced Helicity Reversal of a Single Skyrmionic Bubble Chain in a Nanostructured Frustrated Magnet

Authors: Zhipeng Hou, Qiang Zhang, Xichao Zhang, Guizhou Xu, Jing Xia, Bei Ding, Hang Li, Senfu Zhang, Nitin M Batra, Pedro M. F. J. Costa, Enke Liu, Guangheng Wu, Motohiko Ezawa, Xiaoxi Liu, Yan Zhou, Xixiang Zhang, Wenhong Wang

Abstract: Helicity indicates the in-plane magnetic-moment swirling direction of a skyrmionic configuration. The ability to reverse the helicity of a skyrmionic bubble via purely electrical means has been predicted in frustrated magnetic systems, however its experimental observation has remained challenging. Here, we experimentally demonstrate the current-driven helicity reversal of the skyrmionic bubble in… ▽ More Helicity indicates the in-plane magnetic-moment swirling direction of a skyrmionic configuration. The ability to reverse the helicity of a skyrmionic bubble via purely electrical means has been predicted in frustrated magnetic systems, however its experimental observation has remained challenging. Here, we experimentally demonstrate the current-driven helicity reversal of the skyrmionic bubble in a nanostructured frustrated Fe3Sn2 magnet. The critical current density required to trigger the helicity reversal is 109 - 1010 A/m2, with a corresponding pulse-width varying from 1 μs to 100 ns. Computational simulations reveal that both the pinning effect and dipole-dipole interaction play a crucial role in the helicity-reversal process. △ Less

Submitted 24 November, 2019; originally announced November 2019.

Comments: Accepted by Advanced Materials

Journal ref: Advanced Materials 32, 1904815 (2020)

Understanding Basic Concepts of Topological Insulators Through Su-Schrieffer-Heeger (SSH) Model

Authors: Navketan Batra, Goutam Sheet

Abstract: Topological insulators are a new class of materials that have attracted significant attention in contemporary condensed matter physics. They are different from the regular insulators and they display novel quantum properties that also involve the idea of `topology', an area of mathematics. Some of the fundamental ideas behind the topological insulators, particularly in low-dimensional condensed ma… ▽ More Topological insulators are a new class of materials that have attracted significant attention in contemporary condensed matter physics. They are different from the regular insulators and they display novel quantum properties that also involve the idea of `topology', an area of mathematics. Some of the fundamental ideas behind the topological insulators, particularly in low-dimensional condensed matter systems such as poly-acetylene chains, can be understood using a simple one-dimensional toy model popularly known as the Su-Schrieffer-Heeger model or the SSH model. This model can also be used as an introduction to the topological insulators of higher dimensions. Here we give a concise description of the SSH model along with a brief review of the background physics and attempt to understand the ideas of topological invariants, edge states, and bulk-boundary correspondence using the model. △ Less

Submitted 20 June, 2019; originally announced June 2019.

Comments: To appear in 'Resonance: Journal of Science Education' published by Indian Academy of Sciences

Journal ref: Resonance, 25 765-786 (2020)

Topological Transitions in a Model for Proximity Induced Superconductivity

Authors: Navketan Batra, Swagatam Nayak, Sanjeev Kumar

Abstract: Using a prototype model for proximity induced superconductivity on a bilayer square lattice, we show that interlayer tunneling can drive change in topology of the Bogoliubov quasiparticle bands. Starting with topologically trivial superconductors, transitions to a non-trivial $p_x + {\rm i} p_y$ state and back to another trivial state are discovered. We characterize these phases in terms of edge-s… ▽ More Using a prototype model for proximity induced superconductivity on a bilayer square lattice, we show that interlayer tunneling can drive change in topology of the Bogoliubov quasiparticle bands. Starting with topologically trivial superconductors, transitions to a non-trivial $p_x + {\rm i} p_y$ state and back to another trivial state are discovered. We characterize these phases in terms of edge-state spectra and Chern indices. We show that these transitions can also be controlled by experimentally viable control parameters, the bandwidth of the metallic layer and the gate potential. Insights from our results on a simple model for proximity induced superconductivity may open up a new route to discover topological superconductors. △ Less

Submitted 7 February, 2019; originally announced February 2019.

Comments: 8 pages, 6 figures

Journal ref: Phys. Rev. B 100, 214517 (2019)

Nature of low dimensional structural modulations and relative phase stability in MoS2/WS2-ReS2 transition metal dichalcogenide alloys

Authors: R. Sahu, U. Bhat, N. M. Batra, H. Sharona, B. Vishal, S. Sarkar, S. Assa Aravindh, S. C. Peter, I. S. Roqan, P. M. F. J. D. Costa, R. Datta

Abstract: We report on the various types of Peierls like two dimensional structural modulations and relative phase stability of 2H and 1T poly-types in MoS2-ReS2 and WS2-ReS2 alloy system. Theoretical calculation predicts a polytype phase transition cross over at ~50 at.% of Mo and W in ReS2 in both monolayer and bulk form, respectively. Experimentally, two different types of structural modulations at 50% a… ▽ More We report on the various types of Peierls like two dimensional structural modulations and relative phase stability of 2H and 1T poly-types in MoS2-ReS2 and WS2-ReS2 alloy system. Theoretical calculation predicts a polytype phase transition cross over at ~50 at.% of Mo and W in ReS2 in both monolayer and bulk form, respectively. Experimentally, two different types of structural modulations at 50% and a modulation corresponding to trimerization at 75% alloy composition is observed for MoS2-ReS2 and only one type of modulation is observed at 50% WS2-ReS2 alloy system. The 50% alloy system is found to be a suitable monolithic candidate for metal semiconductor transition with minute external perturbation. ReS2 is known to be in 2D Peierls distorted 1Td structure and forms a chain like superstructure. Incorporation of Mo and W atoms in the ReS2 lattice modifies the metal-metal hybridization between the cations and influences the structural modulation and electronic property of the system. The results offer yet another effective way to tune the electronic structure and poly-type phases of this class of materials other than intercalation, strain, and vertical stacking arrangement. △ Less

Submitted 2 November, 2016; originally announced November 2016.