arXiv subjects

Bhaskaran Muralidharan

Publications and source records attributed to Bhaskaran Muralidharan.

At least 19 recordsLinked to original sources

arXiv2026

Current cross-correlations as probes for poor man's Majorana states

The minimal Kitaev chain that emulates a topological superconductor with three quantum dots offers a tunable platform for potentially hosting poor man's Majorana (PMM) modes. Asserting the need to go beyond differential conductance spectroscopy, we introduce current-current correlations as a viable framework for verifying their true non-locality. The robustness of the PMM modes, specifically with respect to delocalization as the system is tuned away from sweet spots, we show, is embedded in the relative magnitudes of the nonlocal transport processes. This aspect is adeptly captured by current cross-correlations, whose features show remarkable stability around the PMM sweet spot, specifically with respect to the detuning of an outer dot. We establish this as a prominent feature and a diagnostic for true PMMs even in the short chain limit. Our results accentuate the need for current cross-correlation measurements as a diagnostic framework for unambiguously verifying true non-locality of entangled states as well as topologically protected states.

cond-mat.mes-hall↗

arXiv2026

Do single-shot projective readouts necessarily estimate the $T_1$ lifetime ?

When single-shot qubit readout protocols are adapted for multilevel systems, theoretical $T_1$ lifetime calculations often fall short of capturing the experimental lifetime trends. We identify extrinsic population dynamics as the fundamental origin of this disparity, establishing that the lifetime estimates can, in certain operating regions, be distinct from the intrinsic $T_1$ time. We clarify these aspects with an integrated theory to address recent measurements [Nat. Nano, 20, 494, (2025)] on spin-valley states in bilayer graphene. While confirming that phonon and Johnson noise are the dominant intrinsic sources, we show that the inclusion of extrinsic factors provide the critical match to the experimental estimates. The extrinsic factors also effectuate violations of generalized Mathiessen's rules. With an improved handle on the design space, a revised readout protocol to estimate the $T_1$ lifetime of the valley qubit is proposed.

cond-mat.mes-hall↗

arXiv2026

Percolative Instabilities and Sparse-Limit Fractality in 1T-TaS$_2$

The low-temperature metallic phase of 1T-TaS2 may originate from current- and voltage-driven destabilization of the commensurate charge density wave (CDW) in a strongly correlated Mott insulator, alongside the robust yet rarely realized influence of intrinsic electronic distortions. Electrical pulse-driven transport, combined with second harmonic response, reveals abrupt switching, negative differential resistance (NDR), and multiscale domain-wall reorganization. The free energy analysis identifies a critical order parameter threshold for the Mott-metal transition, with scaling exponents (β approx 1.3) consistent with 2D percolation. The sparse limit fractal dimension D_{f} approx 0.3 at 10 K, rising to approx 0.9 at 300 K, reflects the hierarchical evolution of the conductive pathways throughout the temperature. These findings establish a direct connection between fractal percolation, pulse-induced instabilities, and correlated electron transport, offering a framework for controlled access to non-equilibrium phase transitions in low-dimensional quantum materials.

cond-mat.mes-hall↗

arXiv2026

Image Synthesis Using Spintronic Deep Convolutional Generative Adversarial Network

The computational requirements of generative adversarial networks (GANs) exceed the limit of conventional Von Neumann architectures, necessitating energy efficient alternatives such as neuromorphic spintronics. This work presents a hybrid CMOS-spintronic deep convolutional generative adversarial network (DCGAN) architecture for synthetic image generation. The proposed generative vision model approach follows the standard framework, leveraging generator and discriminators adversarial training with our designed spintronics hardware for deconvolution, convolution, and activation layers of the DCGAN architecture. To enable hardware aware spintronic implementation, the generator's deconvolution layers are restructured as zero padded convolution, allowing seamless integration with a 6-bit skyrmion based synapse in a crossbar, without compromising training performance. Nonlinear activation functions are implemented using a hybrid CMOS domain wall based Rectified linear unit (ReLU) and Leaky ReLU units. Our proposed tunable Leaky ReLU employs domain wall position coded, continuous resistance states and a piecewise uniaxial parabolic anisotropy profile with a parallel MTJ readout, exhibiting energy consumption of 0.192 pJ. Our spintronic DCGAN model demonstrates adaptability across both grayscale and colored datasets, achieving Fr'echet Inception Distances (FID) of 27.5 for the Fashion MNIST and 45.4 for Anime Face datasets, with testing energy (training energy) of 4.9 nJ (14.97~nJ/image) and 24.72 nJ (74.7 nJ/image).

physics.app-ph↗

arXiv2025

Symmetry driven spin anisotropic magnetotransport in quantum spin Hall insulator WTe2 1T

We present a comprehensive magnetotransport analysis of monolayer 1T WTe2, highlighting the role of nonsymmorphic symmetries in governing edge-state spin behavior. By comparing the electronic transmission in nanoribbons with edges along the crystallographic y and x directions, our analysis reveals a pronounced anisotropy in the magnetic field response. The y-edge ribbon exhibits significant spin splitting of edge-state bands in both energy and momentum space, along with a strong angular dependence of the conductance. The observed magnetotransport response indicates a spin quantization axis that aligns with the out-of-plane spin quantization axis reported in previous experimental studies. In contrast, the x edge ribbon shows negligible spin splitting under magnetic fields, which is attributed to nonsymmorphic symmetries such as glide mirror and screw rotation, that protects degeneracies along the Gamma X direction, even when time-reversal symmetry is broken. The energy-resolved current density and angular transmission analyses confirm that this anisotropy originates from edge states, while bulk states remain largely insensitive to the field orientation. Our results establish direct transport-spectroscopy based evidence of nonsymmorphic-symmetry-protected spin degeneracy in the 1T WTe2, and underscores its promise for spintronic devices that leverage symmetry-protected and directionally selective transport channels.

cond-mat.mes-hall↗

arXiv2025

Comparative Study of Strain-Engineered Thermoelectric Performance of 2D-Xene Nanoribbons

The quest for efficient and scalable thermoelectric materials has catalyzed intense interest in quasi 1D nanoribbons, where reduced dimensionality and structural tunability can decouple key transport parameters to enhance energy conversion. In this work, we present a unified comparative study of the thermopower in armchair nanoribbons derived from five archetypal 2D materials: graphene, silicene, germanene, stanene and phosphorene. Using a tight binding model parametrized by first principles inputs and solved within the Landauer Buttiker formalism, we compute strain and width dependent thermopower across nanoribbons classified by width families (3p, 3p+1, 3p+2) over a wide range of uniaxial tensile strain. Our results reveal that thermoelectric behavior is governed by a complex interplay of bandgap evolution, chemical potential asymmetry, and quantum confinement. While graphene and silicene exhibit pronounced family and width sensitive thermopower enhancement under moderate strain, heavier Xenes such as germanene and stanene show diminished responses. In particular, phosphorene nanoribbons emerge as exceptional, exhibiting remarkably high thermopower (62 kB/e), a consequence of their large, persistent bandgap and anisotropic electronic structure. Across all systems, the 3p+2 family transitions from near-metallic to semiconducting under strain, enabling dramatic activation of thermopower in previously inactive configurations. This systematic cross material analysis delineates the design principles for the optimization of TE in 1D nanoribbons, highlighting the strategic use of width control and strain engineering. Our findings identify phosphorene as an intrinsically superior thermoelectric material and position strained Xene nanoribbons as promising candidates for tunable, low-dimensional thermoelectric devices.

cond-mat.mes-hall↗

arXiv2025

Rashba-induced spin Hall response in a disordered $WTe_2$ four-terminal structure

The paramount acumen for controlling spin transport properties in nonmagnetic materials is the usage of spin-orbit coupling (SOC). We propose a model to calculate the spin hall angle (SHA) for the elemental transition metal dichalcogenide compound, $WTe_2$ entrenched on the intrinsic Rashba SOC. This model, is based on the Landauer-Buttiker formalism for quantum transport, and the $4$-terminal device setup with the presence of disorder from random onsite potential fluctuations. The SHA, including the mean and RMS values, also illustrate the mesoscopic oscillations, and the values obtained are $25\%$ and $30\%$, respectively. The variation pattern of charge and spin current, along with the mean and spin Hall conductance, can be a comparative measure for other TMDs and monolayer Xenes. To validate our outcomes, we compare our results with experimental data and numerically extract real-space simulation results based on the nearest-neighbor tight binding (NNTB) model. Also our results are in line with the scaling theory of localization. This work sets the stage to calculate the spin Hall angle and spin Hall conductivity for other elemental monolayer Xenes and TMDs, considering the intrinsic scattering mechanisms. An extension of this work will be to explore the possible spintronics applications for extrinsic scattering, including side-jump and skew-jump scattering processes.

cond-mat.mes-hall↗

arXiv2024

Steady-state dynamics and non-local correlations in thermoelectric Cooper pair splitters

Recent experiments on Cooper pair splitters using superconductor-quantum dot hybrids have embarked on creating entanglement in the solid-state, by engineering the sub-gap processes in the superconducting region. Using the thermoelectric Cooper pair splitter setup [Nat. Comm., 12, 21, (2021)] as a prototype, we present a comprehensive analysis of the fundamental components of the observed transport signal, aiming to critically clarify the operating regimes and confirm the nonlocal and nonclassical nature of correlations arising from crossed Andreev processes. By making a nexus with quantum discord, we identify operating points of nonlocal quantum correlations in the CPS device -- information that cannot be extracted from the transport signal alone. A notable consequence of our analysis is the finding that contact-induced level broadening of the quantum dot's discrete energy spectrum, along with its hybridization with the superconducting segment, can lead to shifted resonances in the crossed Andreev process as well as a parity reversal in the thermoelectric current. Our work thereby provides detailed insights into the gate voltage control of the quantum correlations in superconducting-hybrid Cooper pair splitters, revealing new avenues for harnessing quantum correlations in solid-state systems.

cond-mat.mes-hall↗

arXiv2024

On the microscopics of proximity effects in one-dimensional superconducting hybrid systems

Investigating the microscopic details of the proximity effect is crucial for both key experimental applications and fundamental inquiries into nanoscale devices featuring superconducting elements. In this work, we develop a framework motivated by experiments to study induced superconducting correlations in hybrid nanoscale devices featuring layered superconductor-normal heterostructures using the Keldysh non-equilibrium Green's functions. Following a detailed method for analyzing the induced pair amplitude in a prototypical one-dimensional hybrid, we provide insights into the proximity effect within and outside the Andreev approximation. Our analysis also uncovers a disorder-induced crossover in the correlation patterns of the system. By elucidating the spectral distribution of the induced pair amplitude, we investigate the pair correlations established in a recent experiment [Phys.Rev.Lett.128,127701], providing a theoretical basis for the enhanced Cooper pair injection demonstrated through the lens of the induced pair correlations, thereby establishing the promise of our methods in guiding new experiments in hybrid quantum devices.

cond-mat.mes-hall↗

arXiv2024

Unifying recent experiments on spin-valley locking in TMDC quantum dots

The spin-valley or Kramers qubit promises significantly enhanced spin-valley lifetimes due to strong coupling of the electrons' spin to their momentum (valley) degrees of freedom. In transition metal dichalcogenides (TMDCs) such spin-valley locking is expected to be particularly strong owing to the significant intrinsic spin-orbit coupling strength. Very recently, a small number of experiments on TMDC quantum dots have put forth evidence for spin-valley locking for the first time at the few-electron limit. Employing quantum transport theory, here we numerically simulate their ground- and excited-state transport spectroscopy signatures in a unified theoretical framework. In doing so, we reveal the operating conditions under which spin-valley locking occurs in TMDC quantum dots, thereby weaving the connection between intrinsic material properties and the experimental data under diverse conditions. Our simulations thus provide a predictive modeling tool for TMDC quantum dots at the few-electron limit allowing us to deduce from experiments the degree of spin-valley locking based on the SOC strength, inter-valley mixing, and the spin and valley $g$-factors. Our theoretical analysis provides an important milestone towards the next challenge of experimentally confirming valley-relaxation times using single-shot projective measurements

cond-mat.mes-hall↗

arXiv2024

A Comprehensive Convolutional Neural Network Architecture Design using Magnetic Skyrmion and Domain Wall

Spintronic-based neuromorphic hardware offers high-density and rapid data processing at nanoscale lengths by leveraging magnetic configurations like skyrmion and domain walls. Here, we present the maximal hardware implementation of a convolutional neural network (CNN) based on a compact multi-bit skyrmion-based synapse and a hybrid CMOS domain wall-based circuit for activation and max-pooling functionalities. We demonstrate the micromagnetic design and operation of a circular bilayer skyrmion system mimicking a scalable artificial synapse, demonstrated up to 6-bit (64 states) with an ultra-low energy consumption of 0.87 fJ per state update. We further show that the synaptic weight modulation is achieved by the perpendicular current interaction with the labyrinth-maze like uniaxial anisotropy profile, inducing skyrmionic gyration, thereby enabling long-term potentiation (LTP) and long-term depression (LTD) operations. Furthermore, we present a simultaneous rectified linear (ReLU) activation and max pooling circuitry featuring a SOT-based domain wall ReLU with a power consumption of 4.73 $μ$W. The ReLU function, stabilized by a parabolic uniaxial anisotropy profile, encodes domain wall positions into continuous resistance states coupled with the HSPICE circuit simulator. Our integrated skyrmion and domain wall-based spintronic hardware achieves 98.07% accuracy in convolutional neural network (CNN) based pattern recognition task, consuming 110 mW per image.

cond-mat.mes-hall↗

arXiv2024

Domain wall and Magnetic Tunnel Junction Hybrid for on-chip Learning in UNet architecture

We present spintronic devices based hardware implementation of UNet for segmentation tasks. Our approach involves designing hardware for convolution, deconvolution, rectified activation function (ReLU), and max pooling layers of the UNet architecture. We designed the convolution and deconvolution layers of the network using the synaptic behavior of the domain wall MTJ. We also construct the ReLU and max pooling functions of the network utilizing the spin hall driven orthogonal current injected MTJ. To incorporate the diverse physics of spin-transport, magnetization dynamics, and CMOS elements in our UNet design, we employ a hybrid simulation setup that couples micromagnetic simulation, non-equilibrium Green's function, SPICE simulation along with network implementation. We evaluate our UNet design on the CamVid dataset and achieve segmentation accuracies of 83.71$\%$ on test data, on par with the software implementation with 821mJ of energy consumption for on-chip training over 150 epochs. We further demonstrate nearly one order $(10\times)$ improvement in the energy requirement of the network using unstable ferromagnet ($Δ$=4.58) over the stable ferromagnet ($Δ$=45) based ReLU and max pooling functions while maintaining the similar accuracy. The hybrid architecture comprising domain wall MTJ and unstable FM-based MTJ leads to an on-chip energy consumption of 85.79mJ during training, with a testing energy cost of 1.55 $μJ$.

cs.ET↗

arXiv2024

2024 roadmap on 2D topological insulators

2D topological insulators promise novel approaches towards electronic, spintronic, and quantum device applications. This is owing to unique features of their electronic band structure, in which bulk-boundary correspondences enforces the existence of 1D spin-momentum locked metallic edge states - both helical and chiral - surrounding an electrically insulating bulk. Forty years since the first discoveries of topological phases in condensed matter, the abstract concept of band topology has sprung into realization with several materials now available in which sizable bulk energy gaps - up to a few hundred meV - promise to enable topology for applications even at room-temperature. Further, the possibility of combining 2D TIs in heterostructures with functional materials such as multiferroics, ferromagnets, and superconductors, vastly extends the range of applicability beyond their intrinsic properties. While 2D TIs remain a unique testbed for questions of fundamental condensed matter physics, proposals seek to control the topologically protected bulk or boundary states electrically, or even induce topological phase transitions to engender switching functionality. Induction of superconducting pairing in 2D TIs strives to realize non-Abelian quasiparticles, promising avenues towards fault-tolerant topological quantum computing. This roadmap aims to present a status update of the field, reviewing recent advances and remaining challenges in theoretical understanding, materials synthesis, physical characterization and, ultimately, device perspectives.

cond-mat.mes-hall↗

arXiv2024

Insights into optical absorption and dark currents of the 6.1Å Type-II superlattice absorbers for MWIR and SWIR applications

A holistic computational analysis is developed to calculate the quantum efficiency of InAs/GaSb superlattice-based photodetectors. Starting with the electronic band characteristics computed by taking the InSb/GaAs at the interface using the 8-band k.p approach, we demonstrate the impact of InAs and GaSb widths on the bandgap, carrier concentration, and the oscillator strength for type-II superlattice absorbers. Subsequently, the alteration of these characteristics due to the extra AlSb layer in the M superlattice absorber is investigated. Extending our models for determining TE- and TM-polarized optical absorption, our calculations reveal that the TE-polarized absorption shows a substantial influence near the conduction-heavy hole band transition energy, which eventually diminishes, owing to the dominant TM-contribution due to the conduction-light hole band transition. Extending our analysis to the dark currents, we focus mainly on Schokley-Read-Hall recombination and radiative recombination at lower temperatures, and show that Schokley-Read-Hall dominates at low-level injection. We show that short-wavelength and mid-wavelength M superlattice structures exhibit higher quantum efficiency than the corresponding same bandgap type-II superlattice with the lower diffusion dark current. Further, we analyze the density of states blocked by the barrier; crucial for XBp photodetector after absorber examination. Our work thus sets a stage for a holistic and predictive theory aided analysis of the type-II superlattice absorbers, from the atomistic interfacial details all the way to the dark currents and absorption spectra.

cond-mat.mes-hall↗

arXiv2024

Ultrahigh Frequency and Multi-channel Output in Skyrmion Based Nano-oscillator

Spintronic nano-oscillators can generate tunable microwave signals that find a wide range of applications in the field of telecommunication to modern neuromorphic computing systems. Among other spintronic devices, a magnetic skyrmion is a promising candidate for the next generation of low-power devices due to its small size and topological stability. In this work, we propose a multi-channel oscillator design based on the synthetic anti-ferromagnetic (SAF) skyrmion pair. The mitigation of the skyrmion Hall effect in SAF and the associated decimation of the Magnus force endows the proposed oscillator with an ultra-high frequency of 41GHz and a multi-channel frequency output driven by the same current. The ultrahigh operational frequency represents an $\sim$342 times improvement compared to the monolayer single skyrmion oscillator featuring a constant uniaxial anisotropy profile. Using micromagnetic simulations, we demonstrate the effectiveness of our proposed multi-channel oscillator design by introducing multi-channel nanotracks along with multiple skyrmions for enhanced frequency operation. The ultrahigh operational frequency and multi-channel output are attributed to three key factors: The oscillator design accounting for a finite spin-flip length of the spacer (such as Ru) material, tangential velocity proportionality on input spin current along with weak dependence on the radius of rotation of the skyrmion-pair, skyrmion interlocking in the channel enabled by the multi-channel high Ku rings and skyrmion-skyrmion repulsion, therefore resulting ultrahigh frequency and multi-channel outputs.

cond-mat.mes-hall↗

arXiv2024

Inclined junction in monolayer graphene: A gateway toward tailoring valley polarization of Dirac fermions

Generating discernible valley contrasts and segregating valley-indexed fermions in real space within graphene poses considerable challenges due to the isotropic transport within the continuum energy range for degenerate valleys. This study unveils an interesting finding: introducing valley contrast through anisotropic chiral transport in isotropic Dirac systems like graphene, achieved by implementing a tilted PN junction. The tilted junction shifts the angular spectrum to larger angles in accordance with the tilt angle. This modifies the pseudospin-conserved modes across the junction, resulting in valley-resolved chiral transport. This approach not only induces valley splitting within the real space but also preserves the remarkable mobility of fermions, offering distinct advantages over alternative strategies. The comprehensive analysis includes optimizing the experimental setup, scrutinizing factors such as the sequence of the doped region, and examining critical parameters like the tilt angle delta and transition width d across the junction. Surprisingly, an increased transition width enhances transmission, attributed to specular edge scattering. Importantly, the system remains resilient to Anderson short-range edge disorder. The broader implication lies in the transformative potential of inducing analogous anisotropic chiral transport behaviors in isotropic Dirac systems, resembling the characteristics of tilted Dirac-Weyl semimetals, by incorporating a tilted PNJ.

cond-mat.mes-hall↗

arXiv2023

Magneto-transport in the monolayer MoS2 material system for high-performance field-effect transistor applications

Electronic transport in monolayer MoS2 is significantly constrained by several extrinsic factors despite showing good prospects as a transistor channel material. Our paper aims to unveil the underlying mechanisms of the electrical and magneto-transport in monolayer MoS2. In order to quantitatively interpret the magneto-transport behavior of monolayer MoS2 on different substrate materials, identify the underlying bottlenecks, and provide guidelines for subsequent improvements, we present a deep analysis of the magneto-transport properties in the diffusive limit. Our calculations are performed on suspended monolayer MoS2 and MoS2 on different substrate materials taking into account remote impurity and the intrinsic and extrinsic phonon scattering mechanisms. We calculate the crucial transport parameters such as the Hall mobility, the conductivity tensor elements, the Hall factor, and the magnetoresistance over a wide range of temperatures, carrier concentrations, and magnetic fields. The Hall factor being a key quantity for calculating the carrier concentration and drift mobility, we show that for suspended monolayer MoS2 at room temperature, the Hall factor value is around 1.43 for magnetic fields ranging from 0.001 to 1 Tesla, which deviates significantly from the usual value of unity. In contrast, the Hall factor for various substrates approaches the ideal value of unity and remains stable in response to the magnetic field and temperature. We also show that the MoS2 over an Al2O3 substrate is a good choice for the Hall effect detector. Moreover, the magnetoresistance increases with an increase in magnetic field strength for smaller magnetic fields before reaching saturation at higher magnetic fields. The presented theoretical model quantitatively captures the scaling of mobility and various magnetoresistance coefficients with temperature, carrier densities and magnetic fields.

cond-mat.mes-hall↗

arXiv2023

Ultrahigh-performance superlattice mid-infrared nBn photodetectors at high operating temperatures

While advancing a physics-based comprehensive photodetector-simulation model, we propose a novel device design of the mid-wavelength infrared nBn photodetectors by exploiting the inherit flexibility of the $InAs_{1-x}Sb_{x}$ ternary alloy material system. To further explicate the physics of such photodetectors, we calculate several crucial transport and optoelectronic parameters, including the dark current density, absorption coefficient, responsivity, and the quantum efficiency of nBn photodetectors. A remarkable maximum efficiency of 57.39\% is achieved at room temperature at a bias of -0.25 V, coupled with a radiation power density of 50 mW/$cm^{2}$. The proposed structure features a maximum quantum efficiency of 44.18\% and 37.87\% at 60\% and 70\% of the $λ_c$, respectively. Furthermore, a maximum responsivity of 0.9257 A/W is shown within the mid-wavelength infrared spectrum. Through our comprehensive analysis, we also demonstrate that our proposed device design effectively reduces the dark current density by confining the electric field inside the barrier while preserving a superior level of quantum efficiency, and the current in such detectors is diffusion-limited. Insights uncovered here could be of broad interest to critically evaluate the potential of the nBn structures for mid-wavelength infrared photodetectors.

cond-mat.mes-hall↗