papers

Publications (123)

cond-mat.mes-hall2016

Continuous and discontinuous topological quantum phase transitions

Bitan Roy, Pallab Goswami, Jay D. Sau

The continuous quantum phase transition between noninteracting, time-reversal symmetric topological and trivial insulators in three dimensions is described by the massless Dirac fe…

cond-mat.mes-hall2022

Higher-order topological phases on fractal lattices

Sourav Manna, Snehasish Nandy, Bitan Roy

Electronic materials harbor a plethora of exotic quantum phases, ranging from unconventional superconductors to non-Fermi liquids, and, more recently, topological phases of matter.…

cond-mat.mes-hall2016

Ferromagnetism and glassiness on the surface of topological insulators

Chun-Xiao Liu, Bitan Roy, Jay D. Sau

We investigate the nature of the ordering among magnetic adatoms, randomly deposited on the surface of topological insulators. Restricting ourselves to dilute impurity and weak cou…

cond-mat.str-el2025

Strained hyperbolic Dirac fermions: Zero modes, flat bands, and competing orders

Christopher A. Leong, Bitan Roy

Starting from the nearest-neighbor tight-binding model on {10,3} and {14,3} hyperbolic lattices that, for a uniform hopping amplitude, gives rise to emergent Dirac fermions on a cu…

cond-mat.str-el2025

Dynamic mass generation on two-dimensional electronic hyperbolic lattices

Noble Gluscevich, Abhisek Samanta, Sourav Manna +1

Free electrons hopping on hyperbolic lattices embedded on a negatively curved space can foster (a) Dirac liquids, (b) Fermi liquids, and (c) flat bands, respectively characterized…

cond-mat.mes-hall2019

Generalized Triple-Component Fermions: Lattice Model, Fermi arcs, and Anomalous Transport

Snehasish Nandy, Sourav Manna, Dumitru Calugaru +1

We generalize the construction of time-reversal symmetry-breaking triple-component semimetals, transforming under the pseudospin-1 representation, to arbitrary (anti-)monopole char…

cond-mat.str-el2026

Anisotropic marginal Fermi liquid for Coulomb interacting generalized Weyl fermions

Gabriel Malavé, Rodrigo Soto-Garrido, Bitan Roy +1

Owing to the power-law anisotropy in the quasiparticle dispersion, yielding an enhanced density of states, the effects of long range Coulomb interaction get amplified in three-dime…

cond-mat.mes-hall2023

Transport in strained graphene: Interplay of Abelian and axial magnetic fields

Aqeel Ahmed, Sanjib Kumar Das, Bitan Roy

Immersed in external magnetic fields (), buckled graphene constitutes an ideal tabletop setup, manifesting a confluence of time-reversal symmetry () breaking Abeli…

cond-mat.mes-hall2014

Bilayer graphene with parallel magnetic field and twisting: Phases and phase transitions in a highly tunable Dirac system

Bitan Roy, Kun Yang

The effective theory for bilayer graphene (BLG), subject to parallel/in-plane magnetic fields, is derived. With a sizable magnetic field the trigonal warping becomes irrelevant, an…

cond-mat.mes-hall2018

Collisionless Transport Close to a Fermionic Quantum Critical Point in Dirac Materials

Bitan Roy, Vladimir Juricic

Quantum transport close to a critical point is a fundamental, but enigmatic problem due to fluctuations, persisting at all length scales. We report the scaling of optical conductiv…

cond-mat.dis-nn2025

Two-dimensional Disordered Projected Branes: Stability and Quantum Criticality via Dimensional Reduction

Alexander C. Tyner, Vladimir Juricic, Bitan Roy

The interplay of disorder and dimensionality governs the emergence and stability of electronic phases in quantum materials and quantum phase transitions among them. While three-dim…

cond-mat.mes-hall2025

Global phase diagram of two-dimensional dirty hyperbolic Dirac liquids

Christopher A. Leong, Daniel J. Salib, Bitan Roy

Within the framework of the canonical nearest-neighbor tight-binding model for spinless fermions, a family of two-dimensional bipartite hyperbolic lattices hosts massless Diraclike…

cond-mat.str-el2024

Yukawa-Lorentz Symmetry in Non-Hermitian Dirac Materials

Vladimir Juricic, Bitan Roy

Lorentz spacetime symmetry represents a unifying feature of the fundamental forces, typically manifest at sufficiently high energies, while in quantum materials it emerges in the d…

cond-mat.mes-hall2020

Shear viscosity as a probe of nodal topology

Marianne Moore, Piotr Surowka, Vladimir Juricic +1

Electronic materials can sustain a variety of unusual, but symmetry protected touchings of valence and conduction bands, each of which is identified by a distinct topological invar…

cond-mat.mes-hall2020

Non-Abelian anomalies in multi-Weyl semimetals

Renato M. A. Dantas, Francisco Peña-Benitez, Bitan Roy +1

We construct the effective field theory for time-reversal symmetry breaking multi-Weyl semimetals (mWSMs), composed of a single pair of Weyl nodes of (anti-)monopole charge , wi…

cond-mat.mes-hall2022

Projected Topological Branes

Archisman Panigrahi, Vladimir Juricic, Bitan Roy

Nature harbors crystals of dimensionality () only up to three. Here we introduce the notion of \emph{projected topological branes} (PTBs): Lower-dimensional branes embedded in h…

cond-mat.str-el2022

Metals, fractional metals, and superconductivity in rhombohedral trilayer graphene

Andras Szabo, Bitan Roy

Combining mean-field and renormalization group analyses, here we unveil the nature of recently observed superconductivity and parent metallic states in chemically doped rhombohedra…

cond-mat.str-el2021

Interacting spin-3/2 fermions in a Luttinger semimetal: Competing phases and their selection in the global phase diagram

Andras Szabo, Roderich Moessner, Bitan Roy

We compute the effects of electronic interactions on gapless spin-3/2 excitations that in a noninteracting system emerge at a bi-quadratic touching of Kramers degenerate valence an…

cond-mat.mes-hall2020

Strain engineered higher order topological phases for spin-3/2 Luttinger fermions

Andras Szabo, Roderich Moessner, Bitan Roy

Recently, the notion of topological phases of matter has been extended to higher-order incarnations, supporting gapless modes on even lower dimensional boundaries, such as corners…

cond-mat.str-el2017

Competing orders and topology in the global phase diagram of pyrochlore iridates

Pallab Goswami, Bitan Roy, Sankar Das Sarma

Strong electronic interactions and spin orbit coupling can be conducive for realizing novel broken symmetry phases supporting quasiparticles with nontrivial band topology. 227 pyro…

cond-mat.str-el2024

Magnetic catalysis in weakly interacting hyperbolic Dirac materials

Bitan Roy

Due to the linearly vanishing density of states, emergent massless Dirac quasiparticles resulting from the free fermion motion in a family of two-dimensional half-filled bipartite…

cond-mat.mes-hall2025

Nodal pair density waves from a quarter-metal in crystalline graphene multilayers

Sk Asrap Murshed, Bitan Roy

Crystalline graphene heterostructures, namely, Bernal bilayer graphene (BBLG) and rhombohedral trilayer graphene (RTLG), for example, subject to perpendicular electric displacement…

cond-mat.str-el2017

Interacting Weyl fermions: Phases, phase transitions and global phase diagram

Bitan Roy, Pallab Goswami, Vladimir Juricic

We study the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curva…

cond-mat.mes-hall2017

Dissolution of topological Fermi arcs in a dirty Weyl semimetal

Robert-Jan Slager, Vladimir Juricic, Bitan Roy

Weyl semimetals (WSMs) have recently attracted a great deal of attention as they provide condensed matter realization of chiral anomaly, feature topologically protected Fermi arc s…

cond-mat.mes-hall2008

Quantum critical scaling in magnetic field near the Dirac point in graphene

Igor F. Herbut, Bitan Roy

Motivated by the recent measurement of the activation energy at the quantum Hall state at the filling factor f=1 in graphene we discuss the scaling of the interaction-induced gaps…

cond-mat.mes-hall2024

Topological insulators on fractal lattices: A general principle of construction

Daniel J. Salib, Aiden J. Mains, Bitan Roy

Fractal lattices, featuring the self-similarity symmetry, are often geometric descents of parent crystals, possessing all their discrete symmetries (such as rotations and reflectio…

cond-mat.mes-hall2024

Superconductivity in three-dimensional interacting doped topological insulators

Andras L. Szabo, Bitan Roy

Three-dimensional doped Dirac insulators foster simply connected (in both topological and trivial regimes) and annular (deep inside the topological regime) Fermi surfaces (FSs) in…

cond-mat.mes-hall2019

Topological superconductivity of spin-3/2 carriers in a three-dimensional doped Luttinger semimetal

Bitan Roy, Sayed Ali Akbar Ghorashi, Matthew S. Foster +1

We investigate topological Cooper pairing, including gapless Weyl and fully gapped class DIII superconductivity, in a three-dimensional doped Luttinger semimetal. The latter descri…

cond-mat.mes-hall2020

Higher-order topological superconductors in -, -odd quadrupolar Dirac materials

Bitan Roy

The presence or absence of certain symmetries in the normal state (NS) also determines the symmetry of the Cooper pairs. Here we show that parity () and time-reversal…

cond-mat.mes-hall2015

Spontaneous symmetry breaking and quantum Hall valley ordering on the surface of topological hexaborides

Xiao Li, Bitan Roy, S. Das Sarma

A number of strongly correlated heavy fermion compounds, such as samarium (Sm), ytterbium (Yb), plutonium (Pu) hexaboride, are predicted to become topological insulators at low tem…

cond-mat.mes-hall2019

Unconventional superconductivity in nearly flat bands in twisted bilayer graphene

Bitan Roy, Vladimir Juricic

Flat electronic bands can accommodate a plethora of interaction driven quantum phases, since kinetic energy is quenched therein and electronic interactions therefore prevail. Twist…

cond-mat.dis-nn2016

Dirty Weyl semimetals: Stability, phase transition and quantum criticality

Soumya Bera, Jay D. Sau, Bitan Roy

We study the stability of three-dimensional incompressible Weyl semimetals in the presence of random quenched charge impurities. Combining numerical analysis and scaling theory we…

cond-mat.mes-hall2011

Inhomogeneous magnetic catalysis on graphene's honeycomb lattice

Bitan Roy, Igor F. Herbut

We investigate the ordering instability of interacting (and for simplicity, spinless) fermions on graphene's honeycomb lattice by numerically computing the Hartree self-consistent…

cond-mat.mes-hall2020

Dirty higher-order Dirac semimetal: Quantum criticality and bulk-boundary correspondence

Andras Szabo, Bitan Roy

We analyze the stability of time-reversal () and lattice four-fold () symmetry breaking three-dimensional higher-order topological (HOT) Dirac semimetals (DSMs)…

cond-mat.mes-hall2013

Theory of unconventional quantum Hall effect in strained graphene

Bitan Roy, Zi-Xiang Hu, Kun Yang

We show through both theoretical arguments and numerical calculations that graphene discerns an unconventional sequence of quantized Hall conductivity, when subject to both magneti…

cond-mat.str-el2019

Unifying Interacting Nodal Semimetals: A New Route to Strong Coupling

Shouvik Sur, Bitan Roy

We propose a general framework for constructing a large set of nodal-point semimetals by tuning the number of linearly () and (at most) quadratically () dispersing direct…

cond-mat.str-el2018

Quantum Multicriticality near the Dirac-Semimetal to Band-Insulator Critical Point in Two Dimensions: A Controlled Ascent from One Dimension

Bitan Roy, Matthew S. Foster

We compute the effects of generic short-range interactions on gapless electrons residing at the quantum critical point separating a two-dimensional Dirac semimetal (DSM) and a symm…

cond-mat.str-el2018

Itinerant quantum multi-criticality of two dimensional Dirac fermions

Bitan Roy, Pallab Goswami, Vladimir Juricic

We analyze emergent quantum multi-criticality for strongly interacting, massless Dirac fermions in two spatial dimensions () within the framework of Gross-Neveu-Yukawa models,…

cond-mat.mes-hall2014

Surface Theory of a Family of Topological Kondo Insulators

Bitan Roy, Jay D. Sau, Maxim Dzero +1

A low-energy theory for the helical metallic states, residing on the surface of cubic topological Kondo insulators, is derived. Despite our analysis being primarily focused on a pr…

cond-mat.supr-con2014

Axionic superconductivity in three dimensional doped narrow gap semiconductors

Pallab Goswami, Bitan Roy

We consider the competition between the conventional s-wave and the triplet Balian-Werthamer or the B-phase pairings in the doped three dimensional narrow gap semiconductors, such…

cond-mat.mes-hall2026

Observation of dislocation bound states and skin effects in non-Hermitian Chern insulators

Jia-Xin Zhong, Bitan Roy, Yun Jing

The confluence of non-Hermitian (NH) topology and crystal defects has culminated significant interest, yet its experimental exploration has been limited due to the challenges invol…

cond-mat.mes-hall2026

Color degeneracy of competing orders near topological defects cores in planar quadratic band touching systems

Bitan Roy

We study two-dimensional fermionic systems, displaying quadratic band touching in the normal state, in the presence of vortices and skyrmions of insulating and superconducting mass…

cond-mat.str-el2009

Theory of interacting electrons on the honeycomb lattice

Igor F. Herbut, Vladimir Juricic, Bitan Roy

The low-energy theory of electrons interacting via repulsive short-range interactions on graphene's honeycomb lattice at half filling is presented. The exact symmetry of the Lagran…

cond-mat.mes-hall2014

index for gapless fermionic modes in the vortex core of three dimensional paired Dirac fermions

Bitan Roy, Pallab Goswami

We consider the gapless modes along the vortex line of the fully gapped, momentum independent paired states of three-dimensional Dirac fermions. For this, we require the solution o…

cond-mat.mes-hall2021

Topolectric circuits: Theory and construction

Junkai Dong, Vladimir Juricic, Bitan Roy

We highlight a general theory to engineer arbitrary Hermitian tight-binding lattice models in electrical LC circuits, where the lattice sites are replaced by the electrical nodes,…

cond-mat.mes-hall2010

Unconventional superconductivity on honeycomb lattice: the theory of Kekule order parameter

Bitan Roy, Igor F. Herbut

A spatially non-uniform superconducting phase is proposed as the electronic variational ground state for the attractive interactions between nearest neighbors on graphene's honeyco…

cond-mat.mes-hall2017

Optical conductivity of an interacting Weyl liquid in the collisionless regime

Bitan Roy, Vladimir Juricic

Optical conductivity (OC) can serve as a measure of correlation effects in a wide range of condensed matter systems. We here show that the long-range tail of the Coulomb interactio…

cond-mat.supr-con2024

Noncrystalline topological superconductors

Sourav Manna, Sanjib Kumar Das, Bitan Roy

Topological insulators, featuring bulk-boundary correspondence, have been realized on a large number of noncrystalline materials, among which amorphous network, quasicrystals and f…

cond-mat.mes-hall2016

Note on "Quantum superconducting criticality in graphene and topological insulators"

Bitan Roy, Vladimir Juricic, Igor F. Herbut

We correct our previous conclusion regarding the fate of a charged quantum critical point across the superconducting transition for two dimensional massless Dirac fermion. Within t…

cond-mat.mes-hall2013

Topological insulators in strained graphene at weak interaction

Bitan Roy, Igor F. Herbut

The nature of the electronic ground states in strained undoped graphene at weak interaction between electrons is discussed. After providing a lattice realization of the strain-indu…

cond-mat.str-el2025

Yukawa-Lorentz symmetry of interacting non-Hermitian birefringent Dirac fermions

Sk Asrap Murshed, Bitan Roy

The energy spectra of linearly dispersing gapless spin-3/2 Dirac fermions display birefringence, featuring two effective Fermi velocities, thus breaking the space-time Lorentz symm…

cond-mat.mes-hall2017

Global phase diagram of a three dimensional dirty topological superconductor

Bitan Roy, Yahya Alavirad, Jay D. Sau

We investigate the phase diagram of a three-dimensional, time-reversal symmetric topological superconductor in the presence of charge impurities and random -wave pairing. Combin…

cond-mat.str-el2013

Classification of massive and gapless phases in bilayer graphene

Bitan Roy

We here classify of all the fully gapped \emph{massive} and \emph{gapless} phases in bilayer graphene. The effective low energy theory in bilayer graphene is constructed, and vario…

cond-mat.mes-hall2014

Competing charge-density-wave, magnetic and topological ground states at and near Dirac points in graphene in axial magnetic fields

Bitan Roy, Jay D. Sau

In the presence of axial magnetic fields that can be realized in deliberately buckled monolayer graphene, quasi-relativistic Dirac fermions may find themselves in a variety of brok…

cond-mat.str-el2018

Incompressible Even Denominator Fractional Quantum Hall States in the Zeroth Landau Level of Monolayer Graphene

Sujit Narayanan, Bitan Roy, Malcolm P. Kennett

Incompressible even denominator fractional quantum Hall states at fillings and have been recently observed in monolayer graphene. We use…

cond-mat.mes-hall2014

Migdal's theorem and electron-phonon vertex corrections in Dirac materials

Bitan Roy, Jay Deep Sau, S. Das Sarma

Migdal's theorem plays a central role in the physics of electron-phonon interactions in metals and semiconductors, and has been extensively studied theoretically for parabolic band…

cond-mat.mes-hall2019

Magnetotransport in multi-Weyl semimetals: A kinetic theory approach

Renato M. A. Dantas, Francisco Peña-Benitez, Bitan Roy +1

We study the longitudinal magnetotransport in three-dimensional multi-Weyl semimetals, constituted by a pair of (anti)-monopole of arbitrary integer charge (), with and…

cond-mat.mes-hall2022

Non-Hermitian dislocation modes: Stability and melting across exceptional points

Archisman Panigrahi, Roderich Moessner, Bitan Roy

The traditional bulk-boundary correspondence assuring robust gapless modes at the edges and surfaces of insulating and nodal topological materials gets masked in non-Hermitian (NH)…

cond-mat.mes-hall2016

Half vortex and fractional electrical charge in two dimensions

Bitan Roy, Igor F. Herbut

Despite fermion doubling, a two-dimensional quasi-relativistic spin-1/2 system can still lead to true fractionalization of electrical charge, when a massive ordered phase supports…

cond-mat.mes-hall2014

Strain-induced time-reversal odd superconductivity in graphene

Bitan Roy, Vladimir Juricic

Time-reversal symmetry breaking superconductors are exotic phases of matter with fascinating properties, which are, however, encountered rather sparsely. Here we identify the possi…

cond-mat.dis-nn2015

Diffusive Quantum Criticality in Three Dimensional Disordered Dirac Semimetals

Bitan Roy, S. Das Sarma

Three dimensional Dirac semimetals are stable against weak potential disorder, but not against strong disorder. In the language of renormalization group, such stability stems from…

cond-mat.mes-hall2023

Topologically distinct atomic insulators

Sanjib Kumar Das, Sourav Manna, Bitan Roy

Topological classification of quantum solids often (if not always) groups all trivial atomic or normal insulators (NIs) into the same featureless family. As we argue here, this is…

cond-mat.str-el2014

Disordered and interacting parabolic semimetals in two and three dimensions

Hsin-Hua Lai, Bitan Roy, Pallab Goswami

A clean noninteracting parabolic semimetal is characterized by quadratic band touching between the conduction and the valence bands at isolated diabolic points in the Brillouin zon…

cond-mat.mes-hall2025

Non-unitary time dynamics of topological modes in open planar quantum systems

Saakshi Porwal, Bitan Roy

Nontrivial topological invariant of bulk electronic wavefunctions in two-dimensional quantum crystals leaves its footprints on the edge, dislocation, and corner modes. Here we inve…

cond-mat.mes-hall2014

Chiral Symmetry Breaking and the Quantum Hall Effect in Monolayer Graphene

Bitan Roy, Malcolm P. Kennett, S. Das Sarma

Monolayer graphene in a strong magnetic field exhibits quantum Hall states at filling fractions and that are not explained within a picture of noninteracting el…

cond-mat.mes-hall2022

Competing orders and cascade of degeneracy lifting in doped Bernal bilayer graphene

Andras Szabo, Bitan Roy

Motivated by recent experiments [H. Zhou, \emph{et al.}, Science {\bf 375}, 774 (2022) and S. C. de la Barrera, \emph{et al.}, arXiv:2110.13907], here we propose a general mechanis…

cond-mat.mes-hall2015

Magnetic catalysis and axionic charge-density-wave in Weyl semimetals

Bitan Roy, Jay D. Sau

Three-dimensional Weyl and Dirac semimetals can support a chiral-symmetry-breaking, fully gapped, charge-density-wave order even for sufficiently weak repulsive electron-electron i…

cond-mat.mes-hall2023

Inner Skin Effects on Non-Hermitian Topological Fractals

Sourav Manna, Bitan Roy

Non-Hermitian (NH) crystals, quasicrystals and amorphous network display an accumulation of a macroscopic number of states near one of its specific interfaces with vacuum, such as…

cond-mat.str-el2021

Extended Hubbard model in undoped and doped monolayer and bilayer graphene: Selection rules and organizing principle among competing orders

Andras Szabo, Bitan Roy

Performing a leading-order renormalization group analysis, here we compute the effects of generic local or short-range electronic interactions in monolayer and Bernal bilayer graph…

cond-mat.mes-hall2014

Zero-modes and global antiferromagnetism in strained graphene

Bitan Roy, Fakher F. Assaad, Igor F. Herbut

A novel magnetic ground state is reported for the Hubbard Hamiltonian in strained graphene. When the chemical potential lies close to the Dirac point, the ground state exhibits loc…

cond-mat.dis-nn2016

Note on "Diffusive quantum criticality in three-dimensional disordered Dirac semimetals"

Bitan Roy, S. Das Sarma

We correct erroneous conclusions from Ref.[1] regarding the values of various critical exponents, calculated to the two-loop order, and argue that -expansion near two spatial d…

cond-mat.mes-hall2025

Charge-density waves and stripes in quarter metals of graphene heterostructures

Sk Asrap Murshed, Bitan Roy

Motivated by recent experiments, here we identify valley-coherent charge-density wave (VC-CDW) order in the non-degenerate quarter-metal for the entire family of chirally-stacked $…

cond-mat.str-el2012

Conserved charges of order-parameter textures in Dirac systems

Igor F. Herbut, Chi-Ken Lu, Bitan Roy

A simple expression for the induced fermion current in the presence of a texture in mass-order-parameters in two-dimensional condensed-matter Dirac systems is derived using the rep…

cond-mat.mes-hall2018

From Birefringent Electrons to a Marginal or Non-Fermi Liquid of Relativistic Spin-1/2 Fermions: An Emergent Superuniversality

Bitan Roy, Malcolm P. Kennett, Kun Yang +1

We present the quantum critical theory of an interacting nodal Fermi-liquid of quasi-relativisitc pseudo-spin-3/2 fermions that have a non-interacting birefringent spectrum with tw…

cond-mat.str-el2020

Interacting quantum Hall states in a finite graphene flake and at finite temperature

Hank Chen, Matthew R. C. Fitzpatrick, Sujit Narayanan +2

The integer quantum Hall states at fillings and in monolayer graphene have drawn much attention as they are generated by electron-electron interactions. Here we…

cond-mat.str-el2012

Asymmetric spatial structure of zero modes for birefringent Dirac fermions

Bitan Roy, Peter M. Smith, Malcolm P. Kennett

We study the zero energy modes that arise in an unusual vortex configuration involving both the kinetic energy and an appropriate mass term in a model which exhibits birefringent D…

cond-mat.mes-hall2017

Interacting line-node semimetal: Proximity effect and spontaneous symmetry breaking

Bitan Roy

Effects of short-range electronic interactions in a three-dimensional line-node semimetal that supports linearly dispersing quasiparticles around an isolated loop in the Brillouin…

cond-mat.str-el2026

Hidden-ordered Dirac fermions

Bitan Roy

I propose a Hermitian extension of the Lorentz-symmetric Dirac theory by complementing the associated Hamiltonian with another \emph{masslike} anticommuting Dirac operator. The res…

cond-mat.mes-hall2020

Out of equilibrium higher-order topological insulator: Floquet engineering and quench dynamics

Tanay Nag, Vladimir Juricic, Bitan Roy

Higher-order topological~(HOT) states,~hosting topologically protected modes on lower-dimensional boundaries,~such as hinges and corners, have recently extended the realm of the st…

cond-mat.mes-hall2021

Anomalous and normal dislocation modes in Floquet topological insulators

Tanay Nag, Bitan Roy

Electronic bands featuring nontrivial bulk topological invariant manifest through robust gapless modes at the boundaries, e.g., edges and surfaces. As such this bulk-boundary corre…

cond-mat.str-el2026

Non-Hermitian catalysis of spontaneous symmetry breaking on Euclidean and hyperbolic lattices

Christopher A. Leong, Bitan Roy

Depending on the lattice geometry, the nearest-neighbor (NN) tight-binding model for free fermions gives rise to particle-hole symmetric emergent Dirac liquid, Fermi liquid, and fl…

cond-mat.mes-hall2024

Quantized thermal and spin transports of dirty planar topological superconductors

Sanjib Kumar Das, Bitan Roy

Nontrivial bulk topological invariants of quantum materials can leave their signatures on charge, thermal and spin transports. In two dimensions, their imprints can be experimental…

cond-mat.mes-hall2015

Excitonic and Nematic Instabilities on the Surface of Topological Kondo Insulators

Bitan Roy, Johannes Hofmann, Valentin Stanev +2

We study the effects of strong electron-electron interactions on the surface of cubic topological Kondo insulators (such as samarium hexaboride, SmB). Cubic topological Kondo i…

cond-mat.mes-hall2025

Hybrid symmetry class topological insulators

Sanjib Kumar Das, Bitan Roy

Traditional topological materials belong to different Altland-Zirnbauer symmetry classes (AZSCs) depending on their non-spatial symmetries. Here we introduce the notion of hybrid s…

cond-mat.mes-hall2016

Universal optical conductivity of a disordered Weyl semimetal

Bitan Roy, Vladimir Juricic, Sankar Das Sarma

Topological Weyl semimetals, besides manifesting chiral anomaly, can also accommodate a disorder-driven unconventional quantum phase transition into a metallic phase. A fundamental…

cond-mat.str-el2019

Fermionic multicriticality near Kekulé valence-bond ordering in honeycomb lattice

Bitan Roy, Vladimir Juricic

We analyze the possibility of emergent quantum multicritical points (MCPs) with enlarged chiral symmetry, when strongly interacting gapless Dirac fermions acquire comparable propen…

cond-mat.mes-hall2012

Effective field theory, chiral anomaly and vortex zero modes for odd parity topological superconducting state of three dimensional Dirac materials

Pallab Goswami, Bitan Roy

The low energy quasiparticle dispersion of various narrow gap and gapless semiconductors are respectively described by three dimensional massive and massless Dirac fermions. The th…

cond-mat.mes-hall2021

Dislocation as a bulk probe of higher-order topological insulators

Bitan Roy, Vladimir Juricic

Topological materials occupy the central stage in the modern condensed matter physics because of their robust metallic edge or surface states protected by the topological invariant…

cond-mat.str-el2024

Quantum Electrodynamics of Non-Hermitian Dirac Fermions

Sk Asrap Murshed, Bitan Roy

We develop an effective quantum electrodynamics for non-Hermitian (NH) Dirac materials interacting with photons. These systems are described by nonspatial symmetry protected Lorent…

cond-mat.str-el2013

Quantum superconducting criticality in graphene and topological insulators

Bitan Roy, Vladimir Juricic, Igor F. Herbut

The field theory of the semimetal-superconductor quantum phase transition for graphene and surface states of topological insulators is presented. The Lagrangian possesses the globa…

cond-mat.str-el2025

Axionic quantum criticality of generalized Weyl semimetals

Gabriel Malave, Rodrigo Soto-Garrido, Vladimir Juricic +1

We formulate a field-theoretic description for -dimensional interacting nodal semimetals, featuring dispersion that scales with the linear and th power of momentum along $d_L…

cond-mat.mes-hall2021

Hierarchy of higher-order Floquet topological phases in three dimensions

Tanay Nag, Vladimir Juricic, Bitan Roy

Following a general protocol of periodically driving static first-order topological phases (supporting surface states) with suitable discrete symmetry breaking Wilson-Dirac masses,…

cond-mat.mes-hall2026

Ordinary lattice defects as probes of topology

Aiden J. Mains, Jia-Xin Zhong, Yun Jing +1

In addition to topological lattice defects such as dislocations and disclinations, crystals are also accompanied by unavoidable ordinary defects, devoid of any non-trivial geometry…

cond-mat.mes-hall2025

From local spin nematicity to altermagnets: Footprints of band topology

Sanjib Kumar Das, Bitan Roy

Altermagnets are crystallographic rotational symmetry breaking spin-ordered states, possessing a net zero magnetization despite manifesting Kramer's non-degenerate bands. Here, we…

cond-mat.mes-hall2020

Higher-order topological insulators in amorphous solids

Adhip Agarwala, Vladimir Juricic, Bitan Roy

We identify the possibility of realizing higher order topological (HOT) phases in noncrystalline or amorphous materials. Starting from two and three dimensional crystalline HOT ins…

cond-mat.supr-con2023

Polar hairs of mixed-parity nodal superconductors in Rarita-Schwinger-Weyl metals

Saswata Mandal, Bitan Roy

Linearly dispersing Rarita-Schwinger-Weyl (RSW) fermions featuring two Fermi velocities are the key constituents of itinerant spin-3/2 quantum materials. When doped, RSW metals sus…

cond-mat.mes-hall2014

Theory of integer quantum Hall effect in insulating bilayer graphene

Bitan Roy

A variational ground state for insulating bilayer graphene (BLG), subject to quantizing magnetic fields, is proposed. Due to the Zeeman coupling, the layer anti-ferromagnet (LAF) o…

cond-mat.mes-hall2019

Higher Order Topological Phases: A General Principle of Construction

Dumitru Calugaru, Vladimir Juricic, Bitan Roy

We propose a general principle for constructing higher-order topological (HOT) phases. We argue that if a -dimensional first-order or regular topological phase involves Herm…

cond-mat.str-el2021

Competing magnetic orders and multipolar Weyl fermions in 227 pyrochlore iridates

Konstantinos Ladovrechis, Tobias Meng, Bitan Roy

Owing to comparably strong spin-orbit coupling and Hubbard interaction, iridium based 227 pyrochlore oxides harbor a rich confluence of competing magnetic orders and emergent multi…

cond-mat.supr-con2021

Mixed-parity octupolar pairing and corner Majorana modes in three dimensions

Bitan Roy, Vladimir Juricic

We identify time-reversal symmetry breaking mixed-parity superconducting states that feature eight Majorana corner modes in properly cleaved three-dimensional cubic crystals. Namel…