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Biswajit Karmakar

Publications and source records attributed to Biswajit Karmakar.

At least 19 recordsLinked to original sources
arXiv2026

Emergent Chiral Metal Phase in Compressible Quantum Hall Fluids

We report transmitted conductance measurements between a source and reflection-less contacts connected to a compressible quantum Hall fluid with filling fraction $ν$. We observe that total sum of transmitted conductances universally approaches Hall conductance $ν(e^2/h)$. The universality of this sum rule is established experimentally across integer and fractional quantum Hall regimes, remaining invariant under variation in temperatures, sample geometries, material qualities and quasi-particle interactions. Chiral transport in compressible quantum Hall fluids, characterized by suppressed dissipative transport with a distinct handedness, is confirmed by floating contact measurements. Consequently, this sum rule emerges as a conduction law of the chiral metal phase. Theoretically, we argue that time-reversal-symmetry breaking under a strong magnetic field within this chiral metal gives rise unidirectional trajectories of carriers in a nearly flat potential landscape with point-like disorder potentials, a regime realized when the screening length is smaller than the magnetic length. Within this chiral framework, longitudinal resistance does not originate from bulk dissipation but primarily from the equilibration of electrochemical potentials at the contacts. Our study introduces a new paradigm of chiral transport across a broad class of gapless two-dimensional systems characterized by short-range screening and broken time-reversal symmetry.

cond-mat.mes-hall↗
arXiv2026

Inelastic Self-interacting Dark Matter and LUX-ZEPLIN 248 keV Event in a Dirac Modular Inverse Seesaw

We propose a novel framework that simultaneously addresses the origin of Dirac neutrino masses and the nature of self-interacting dark matter (SIDM). The model is based on an $A_{4}$ modular symmetry to ensure the Diracness of neutrinos as well as the stability of the DM. The neutrino sector realizes a Dirac Inverse Seesaw mechanism where the smallness of the neutrino mass is governed by the vacuum expectation value (VEV) of a singlet scalar $ϕ$. This same scalar couples to a vector-like fermion DM candidate, inducing a tiny Majorana mass splitting that renders the DM pseudo-Dirac and inelastic. Crucially, the scalar also acts as a light mediator for DM self-interactions, potentially solving the small-scale structure problems of Cold DM. In light of the recent 248 keV nuclear-recoil event, LZ230616, observed by LUX-ZEPLIN (LZ) DM direct detection experiment, we demonstrate that our inelastic SIDM parameter space naturally accommodates this signal via endothermic scattering kinematics. Furthermore, the spontaneous breaking of the dark parity required for this inelasticity produces a network of cosmological domain walls. We show that the explicit symmetry breaking needed to safely annihilate these walls generates a stochastic gravitational wave background. The non-holomorphic modular symmetry reduces the free parameters, correlating neutrino observables, addressing DM phenomenology, $ΔN_{\rm eff}$, and gravitational-wave signatures.

hep-ph↗
arXiv2026

CP-conserving SO(3) parameterization of the neutrino mixing matrix

The pattern of neutrino mixing, usually parameterized by the Pontecorvo-Maki-Nakagawa-Sakata $U_{\rm PMNS}$ matrix, still remains a striking puzzle in particle physics. $U_{\rm PMNS}$ is one of six possible products of multiplying three Euler matrices. Here we discuss the neutrino mixing matrix parameterization for three known flavours of neutrinos based on the SO(3) group represented by one three-dimensional rotation matrix $U_{\rm SO3}$ and the CP-conserving phases $δ_{\rm CP}=0^{\circ}$ and $180^\circ$. The mixing matrix $U_{\rm SO3}$ with cyclic order of the Lie group generators implies $δ_{\rm{CP}}=180^\circ$ for clockwise rotation in three dimensions, a viable scenario for normal mass ordering. We determine a range of rotation angles for $U_{\rm SO3}$ which deviate substantially from the almost maximal mixings in the standard $U_{\rm PMNS}$ scenario, yielding `democratic' values for the mixing angles. On the other hand, $δ_{\rm CP}=0^{\circ}$ CP-conserving case supports near-maximal mixing scenario. With the fixed $δ_{\rm CP}$ value, the $U_{\rm SO3}$ parameterization can be validated or falsified by the next generation of neutrinoless double beta decay experiments and puts a stringent constraint on the absolute neutrino mass. The proposed $U_{\rm SO3}$ neutrino mixing parameterization is suited for independent CP-conserving neutrino oscillation experimental analysis.

hep-ph↗
arXiv2025

Collapse of edge reconstruction in compressible Quantum Hall fluid within filling fraction range 2/3 to 1

The edge structure of a gate-defined compressible quantum Hall fluids in the filling fraction range 2/3 to 1 is studied using the three reconstructed $e^2/3h$ fractional edge modes of unity filling integer quantum Hall state. We find that the individually excited partially resolved $e^2/3h$ edge modes of the bulk state equilibrate completely even at higher magnetic field when passing through the gate defined compressible fluid with filling between 2/3 and 1. This result is unexpected because edge reconstruction at the smooth boundary is generally expected due to dominant incompressibility at filling 2/3 and 1/3. Recently such reconstructed edge mode has been reported for the compressible fluid in the filling fraction range 1/3 to 2/3. In contrary, equilibration of fractional edge modes in the compressible fluid within the filling fraction range 2/3 to 1 becomes faster with increasing magnetic field. This anomalous results will stimulate further investigations on edge structure in these complex many body systems.

cond-mat.mes-hall↗
arXiv2025

Discrete dark matter with light Dirac neutrinos

We propose a new realisation of light Dirac neutrino mass and dark matter (DM) within the framework of a non-Abelian discrete flavour symmetry based on $A_4$ group. In addition to $A_4$, we also consider a $Z_2$ and an unbroken global lepton number symmetry $U(1)_L$ to keep unwanted terms away while guaranteeing the Dirac nature of light neutrinos. The field content, their transformations and flavon vacuum alignments are chosen in such a way that the type-I Dirac seesaw generates only one light Dirac neutrino mass while the other two masses arise from scotogenic contributions at one-loop. This leads to the Dirac scoto-seesaw framework, a generalisation of the widely studied scoto-seesaw model to Dirac neutrinos. The symmetry breaking of $A_4$ leaves a remnant $\mathcal{Z}_2$ symmetry responsible for stabilising DM. Dirac nature of light neutrinos introduces additional relativistic degrees of freedom $ΔN_{\rm eff}$ within reach of cosmic microwave background experiments.

hep-ph↗
arXiv2024

Edge reconstruction of compressible Quantum Hall fluid in the filling fraction range 1/3 to 2/3

Edge reconstruction of gate-tunable compressible quantum Hall fluids in the filling fraction range 1/3 to 2/3 is studied by measuring transmitted conductance of two individually excited fractional $e^2/3h$ edge modes of bulk 2/3 fractional quantum Hall fluid. Our findings reveal that the measured transmitted conductance deviates from the fully equilibrated value for the filling fraction range 1/3 to 2/3 of the gate-tunable compressible quantum Hall fluids at higher magnetic fields. This observation suggests that at the boundary of the compressible fluid a reconstructed $e^2/3h$ fractional edge mode is present and the mode does not completely equilibrate with the inner dissipative bulk region. Consequently, this outer reconstructed edge mode supports adiabatic charge transport, allowing non-equilibrated current transport through the compressible region. These studies open new avenues for achieving robust fractional edge modes even in compressible quantum Hall fluids under strong magnetic fields, enhancing our understanding of edge state dynamics in these complex systems.

cond-mat.mes-hall↗
arXiv2024

Neutrino Mixing from a Fresh Perspective

We propose a neutrino mass matrix texture bearing a suitable correlation $m_{22}=-2\,m_{13}$ and study its phenomenological implications. In light of both normal and inverted hierarchies, the texture imposes specific bounds on some observational parameters. As a potential application, the prediction of effective Majorana neutrino mass $m_{ββ}$ is visualized for both hierarchies. To understand the proposed texture from the first principle, we incorporate the type-I+II seesaw mechanism in association with $A_4 \times Z_{10} \times Z_2$ group.

hep-ph↗
arXiv2024

Phenomenology of the flavor symmetric scoto-seesaw model with dark matter and TM$_1$ mixing

We propose a hybrid scoto-seesaw model based on the $A_4$ non-Abelian discrete flavor symmetry. Light neutrino masses come from the tree-level type-I seesaw mechanism and from the one-loop scotogenic contribution accommodating viable dark matter candidates responsible for observed relic abundance of dark matter (DM). Respectively, both these contributions restore the atmospheric and solar neutrino mass scales. With only one right-handed neutrino, the model features specific predictions with the normal ordering of light neutrino masses, the lightest neutrino being massless, and only one relevant CP Majorana phase. The flavor symmetric setup helps us to realize the TM$_1$ mixing scheme with concrete correlations and constraints on the mixing angles and associated CP phases. The framework predicts the atmospheric mixing angle to be in the upper octant with specific ranges $0.531 (0.580) \leq \sin^2θ_{23}\leq 0.544 (0.595)$ and the Dirac CP phase is restricted within the range $\pm(1.44-1.12)$ radian. The Majorana phase is also tightly constrained with a range of $0.82-0.95$ and $1.58-1.67$ radian, which is otherwise unconstrained from neutrino oscillations. Strict predictions on the Majorana phases also yield an accurate prediction for the effective mass parameter for neutrinoless double beta within the range of $1.61-3.85$ meV. The model offers a rich phenomenology regarding DM relic density and direct search constraints, and the fermionic DM scenario has been discussed in detail, estimating its possible connection with the neutrino sector. As an example of the model studies at colliders, the SM Higgs in the diphoton decay channel is examined. The model predicts strictly vanishing $τ\to eγ$, $τ\rightarrow 3e$ decays and testable signals by MEG-II and SINDRUM/Mu3e experiments for the $μ\to e γ$ and $μ\to 3 e$ decays, respectively.

hep-ph↗
arXiv2024

Phenomenology of Lepton Masses and Mixing with Discrete Flavor Symmetries

The observed pattern of fermion masses and mixing is an outstanding puzzle in particle physics, generally known as the flavor problem. Over the years, guided by precision neutrino oscillation data, discrete flavor symmetries have often been used to explain the neutrino mixing parameters, which look very different from the quark sector. In this review, we discuss the application of non-Abelian finite groups to the theory of neutrino masses and mixing in the light of current and future neutrino oscillation data. We start with an overview of the neutrino mixing parameters, comparing different global fit results and limits on normal and inverted neutrino mass ordering schemes. Then, we discuss a general framework for implementing discrete family symmetries to explain neutrino masses and mixing. We discuss CP violation effects, giving an update of CP predictions for trimaximal models with nonzero reactor mixing angle and models with partial $μ-τ$ reflection symmetry, and constraining models with neutrino mass sum rules. The connection between texture zeroes and discrete symmetries is also discussed. We summarize viable higher-order groups, which can explain the observed pattern of lepton mixing where the non-zero $θ_{13}$ plays an important role. We also review the prospects of embedding finite discrete symmetries in the Grand Unified Theories and with extended Higgs fields. Models based on modular symmetry are also briefly discussed. A major part of the review is dedicated to the phenomenology of flavor symmetries and possible signatures in the current and future experiments at the intensity, energy, and cosmic frontiers. In this context, we discuss flavor symmetry implications for neutrinoless double beta decay, collider signals, leptogenesis, dark matter, as well as gravitational waves.

hep-ph↗
arXiv2022

Common origin of $θ_{13}$ and dark matter within the flavor symmetric scoto-seesaw framework

To understand the observed pattern of neutrino masses and mixing as well as to account for the dark matter we propose a hybrid scoto-seesaw model based on the $A_4$ discrete flavor symmetry. In this setup, including at least two heavy right-handed neutrinos is essential to employ the discrete flavor symmetry that mimics once popular tribimaximal neutrino mixing at the leading order via type-I seesaw. The scotogenic contribution then acts as a critical deviation to reproduce the observed value of the reactor mixing angle $θ_{13}$ (within the trimaximal mixing scheme) and to accommodate potential dark matter candidates, pointing towards a common origin of $θ_{13}$ and dark matter. The model predicts the atmospheric angle to be in the upper octant, excludes some regions on the Dirac CP phase, and restricts the Majorana phases too. Further, normal and inverted mass hierarchies can be distinguished for specific values of the relative phases associated with the complex light neutrino mass matrix. Owing to the considered flavor symmetry, contributions coming from the scotogenic mechanism towards the lepton flavor violating decays such as $μ\rightarrow e γ$, $τ\rightarrow e γ$ vanish, and a lower limit on the second right-handed neutrino mass can be obtained. Prediction for the effective mass parameter appearing in the neutrinoless double beta decay falls within the sensitivity of future experiments such as LEGEND-1k and nEXO.

hep-ph↗
arXiv2022

Discrete Flavor Symmetries and Lepton Masses and Mixings

We discuss neutrino mass and mixing models based on discrete flavor symmetries. These models can include a variety of new interactions and non-standard particles such as sterile neutrinos, scalar Higgs singlets and multiplets. We point at connections of the models with leptogenesis and dark matter and the ways to detect the corresponding non-standard particles at intensity and energy frontier experiments.

hep-ph↗
arXiv2021

Flavored Leptogenesis and Neutrino Mass with $A_4$ Symmetry

We propose a minimal $A_4$ flavor symmetric model, assisted by $Z_2 \times Z_3$ symmetry, which can naturally takes care of the appropriate lepton mixing and neutrino masses via Type-I seesaw. It turns out that the framework, originated due to a specific flavor structure, favors the normal hierarchy of light neutrinos and simultaneously narrows down the range of Dirac CP violating phase. It predicts an interesting correlation between the atmospheric mixing angle and the Dirac CP phase too. While the flavor structure indicates an exact degeneracy of the right handed neutrino masses, renormalization group running of the same from a high scale is shown to make it quasi-degenerate and a successful flavor leptogenesis takes place within the allowed parameter space obtained from neutrino phenomenology.

hep-ph↗
arXiv2021

Temperature dependent equilibration of spin orthogonal quantum Hall edge modes

Conductance of the edge modes as well as conductance across the co-propagating edge modes around the ν= 4/3, 5/3 and 2 quantum Hall states are measured by individually exciting the modes. Temperature dependent equilibration rates of the outer unity conductance edge mode are presented for different filling fractions. We find that the equilibration rate of the outer unity conductance mode at ν= 2 is higher and more temperature sensitive compared to the mode at fractional filling 5/3 and 4/3. At lowest temperature, equilibration length of the outer unity conductance mode tends to saturate with lowering filling fraction νby increasing magnetic field B. We speculate this saturating nature of equilibration length is arising from an interplay of Coulomb correlation and spin orthogonality.

cond-mat.mes-hall↗
arXiv2020

Magnetic field dependent equilibration of fractional quantum Hall edge modes

Fractional conductance is measured by partitioning $ν= 1$ edge state using gate-tunable fractional quantum Hall (FQH) liquids of filling 1/3 or 2/3 for current injection and detection. We observe two sets of FQH plateaus 1/9, 2/9, 4/9 and 1/6, 1/3, 2/3 at low and high magnetic field ends of the $ν= 1$ plateau respectively. The findings are explained by magnetic field dependent equilibration of three FQH edge modes with conductance $e^2/3h$ arising from edge reconstruction. The results reveal remarkable enhancement of the equilibration lengths of the FQH edge modes with increasing field.

cond-mat.mes-hall↗
arXiv2019

Planck Scale Origin of Non-zero $θ_{13}$ and Super-WIMP Dark Matter

We study a discrete flavour symmetric scenario for neutrino mass and dark matter under the circumstances where such global discrete symmetries can be explicitly broken at Planck scale, possibly by gravitational effects. Such explicit breaking of discrete symmetries mimic as Planck suppressed operators in the model which can have non-trivial consequences for neutrino and dark matter sectors. In particular, we study a flavour symmetric model which, at renormalisable level, gives rise to tri-bimaximal type neutrino mixing with vanishing reactor mixing angle $θ_{13}=0$, a stable inert scalar doublet behaving like a weakly interacting massive particle (WIMP) and a stable singlet inert fermion which does not interact with any other particles. The introduction of Planck suppressed operators which explicitly break the discrete symmetries, can give rise to the generation of non-zero $θ_{13}$ in agreement with neutrino data and also open up decay channels of inert scalar doublet into singlet neutral inert fermion leading to the realisation of the super-WIMP dark matter scenario. We show that the correct neutrino phenomenology can be obtained in this model while discussing three distinct realisation of the super-WIMP dark matter scenario.

hep-ph↗
arXiv2019

Consequences of $μ$-$τ$ reflection symmetry for $3+1$ neutrino mixing

We investigate the consequences of $μ-τ$ reflection symmetry in presence of a light sterile neutrino for the $3+1$ neutrino mixing scheme. We discuss the implications of total $μ-τ$ reflection symmetry as well partial $μ-τ$ reflection symmetry. For the total $μ-τ$ reflection symmetry we find values of $θ_{23}$ and $δ$ remains confined near $π/4$ and $\pm π/2$ respectively. The current allowed region for $θ_{23}$ and $δ$ in case of inverted hierarchy lies outside the area preferred by the total $μ-τ$ reflection symmetry. However, interesting predictions on the neutrino mixing angles and Dirac CP violating phases are obtained considering partial $μ-τ$ reflection symmetry. We obtain predictive correlations between the neutrino mixing angle $θ_{23}$ and Dirac CP phase $δ$ and study the testability of these correlations at the future long baseline experiment DUNE. We find that while the imposition of $μ-τ$ reflection symmetry in the first column admit both normal and inverted neutrino mass hierarchy, demanding $μ-τ$ reflection symmetry for the second column excludes the inverted hierarchy. Interestingly, the sterile mixing angle $θ_{34}$ gets tightly constrained considering the $μ-τ$ reflection symmetry in the fourth column. We also study consequences of $μ-τ$ reflection symmetry for the Majorana phases and neutrinoless double beta decay.

hep-ph↗
arXiv2018

Dark side of the Seesaw

In an attempt to unfold (if any) a possible connection between two apparently uncorrelated sectors, namely neutrino and dark matter, we consider the type-I seesaw and a fermion singlet dark matter to start with. Our construction suggests that there exists a scalar field mediator between these two sectors whose vacuum expectation value not only generates the mass of the dark matter, but also takes part in the neutrino mass generation. While the choice of $Z_4$ symmetry allows us to establish the framework, the vacuum expectation value of the mediator field breaks $Z_4$ to a remnant $Z_2$, that is responsible to keep dark matter stable. Therefore, the observed light neutrino masses and relic abundance constraint on the dark matter, allows us to predict the heavy seesaw scale as illustrated in this paper.The methodology to connect dark matter and neutrino sector, as introduced here, is a generic one and can be applied to other possible neutrino mass generation mechanism and different dark matter candidate(s).

hep-ph↗