arXiv subjects

Paramita Dutta

Publications and source records attributed to Paramita Dutta.

At least 19 recordsLinked to original sources

arXiv2026

Supercurrent detection and manipulation of topological phase transitions in Shiba-Majorana hybrid systems

The non-Abelian statistics of Majorana zero modes has inspired numerous proposals for their detection and manipulation in topological superconductors. Implementations based on magnetic adatoms deposited on superconductors draw particular attention due to their capabilities for precise atomic manipulation and the control over disorder. Here, we propose a scheme for detecting changes in the ground state parity of a topologically non-trivial adatom system by passing supercurrent through their low-energy modes. We unravel characteristic discontinuities in the critical current driven by zero-energy level crossings. We apply these findings to a setup where the Majorana coupling is mediated by a single control magnetic adatom hosting a Yu-Shiba-Rusinov state, and test the robustness of our results against finite temperatures and different tunneling regimes. Our findings introduce a non-invasive approach for reading out and controlling the ground state parity of Majorana states in Shiba-Majorana hybrid systems.

cond-mat.supr-con↗

arXiv2026

Superconducting order parameter in aperiodic binary systems

Recent discovery of the superconducting ground state in systems lacking perfect periodicity but with long-range ordering has opened up an exciting new avenue for superconductivity based on aperiodic systems. In this work, we explore the scope by theoretically investigating the behavior of the superconducting order parameter (OP) in aperiodic binary systems (ABSs), both Fibonacci and non-Fibonacci type, based on the attractive Hubbard model. We begin with one-dimensional toy model, and for the generality of our findings, we extend our analysis to two-dimensional ABSs. Remarkably, despite the increased dimensionality, the qualitative features of the OP remain largely preserved. By systematically analyzing models generated through various growth rules, we elucidate the influence of aperiodicity on the OP amplitudes and how it evolves towards the periodic limit with the change in the structural pattern. We study the evolution of the OP with respect to the temperature, strength of the interaction, and nearest-neighbor hopping amplitude. Our numerical analysis identifies the most favorable ABS and parameter regime that support enhanced onsite pairing amplitudes. Additionally, we provide a comparative analysis of the superconducting transition temperatures across the range of aperiodic configurations. To gain further insight into these systems, we compute key thermodynamic quantities: the entropy and electronic specific heat, and examine their dependence on the underlying structural sequences. This analysis enables us to determine which ABSs are most conducive to Cooper pair formation.

cond-mat.supr-con↗

arXiv2026

Dive deeper with SUBMARINE: SUB-Mev dArk matter diRect detectIon using bilayer grapheNE

Novel target materials with anisotropic response will play a key role in detecting low-mass dark matter in upcoming experiments. Bilayer graphene is one such material that has been proposed for the detection of sub-MeV mass dark matter particles via electronic excitations. In this work, we calculate scattering rate via a massive mediator in bilayer graphene. With an exposure as small as $\sim$ 0.5 mg-year, bilayer graphene can probe new regions of the parameter space. The anisotropic response function of bilayer graphene leads to a sidereal-day modulation in the scattering rate, depending on its orientation with respect to the Galactic dark matter wind. We find significant modulation in the scattering rate for sub-MeV mass dark matter, demonstrating bilayer graphene's promise for a future experiment. We hope that our work will motivate the community to investigate bilayer graphene as a novel target material, and that it may lead us to discover the particle nature of dark matter.

hep-ph↗

arXiv2026

Proximity-induced superconductivity and emerging topological phases in altermagnet-based heterostructures

We present a theoretical framework for investigating superconducting proximity effect in altermagnet (AM)-superconductor (SC) heterostructures. In general, AMs, characterized by vanishing net magnetization but spin-split electronic spectra, provide a promising platform for realizing unconventional magnetic phases. We consider a two-dimensional $d$-wave AM proximity coupled to a three dimensional ordinary $s$-wave SC. By integrating out the superconducting degrees of freedom, we derive an effective Hamiltonian that describes the proximity-induced modifications in the AM layer in the form of a self-energy. We then derive an effective Green's function to obtain the proximity-induced pairing amplitudes in the AM layer and classify the induced pairing amplitudes according to their parity, frequency, and spin. We find the presence of even-parity singlet and triplet pairing amplitudes in the AM layer. To achieve the odd-parity triplet components, important to realize topological superconductivity, we introduce a layer of Rashba spin-orbit coupling (RSOC) in the heterostructure. We analyse the band topology of this proximity-induced AM-RSOC layer and demonstrate the emergence of both weak and strong topological superconducting phases with edge-localized modes, characterized by winding number and Chern number. These findings highlight the role of AM-SC hybrid setup as a versatile platform for realizing odd-parity triplet pairings and engineering topological superconductivity in two-dimension.

cond-mat.supr-con↗

arXiv2026

Spin polarization and diode effect in thermoelectric current through altermagnet-based superconductor heterostructures

The recent advent of a new class of magnetic material named as {\it altermagnet} (AM), characterized by a combination of momentum-dependent spin splitting with zero net magnetization, has opened up promising prospects for spintronic applications. We theoretically explore how the altermagnetic spin splitting affects the thermoelectric quasiparticle current in AM-based superconducting heterostructures. Our setup comprises of a bilayer system where a $d$-wave AM is proximity coupled to an ordinary $s$-wave superconductor (SC). We calculate the thermoelectric current carried by the quasiparticles applying a finite thermal bias across the junction. The behavior of the thermoelectric current with the system's base temperature and chemical potential is very similar to that in traditional SC heterostructures. Remarkably, the dissipative thermoelectric current found in the AM junction is spin split and thus generates finite spin polarization in the AM-based junction, which can approach $100\%$ spin polarization in the strong altermagnetic phase. We further investigate the thermoelectric current in AM-based Josephson junction (JJ) and illustrate how to achieve almost perfect diode effect in this AM-based JJ characterized by its efficiency $\sim 100\%$ with its sign decided by the strength of the AM, enhancing the potential for spin-caloritronics applications.

cond-mat.supr-con↗

arXiv2026

Emergent superconducting phases in unconventional $p$-wave magnets: Topological superconductivity, Bogoliubov Fermi surfaces and superconducting diode effect

The recent discovery of unconventional momentum-dependent magnetic orders has expanded the landscape of magnetism beyond conventional ferromagnetism and antiferromagnetism. Among them, $p$-wave magnets ($p$WMs) represent a novel class of odd-parity, non-collinear compensated magnetic order that generates spin-split electronic bands. In this work, our theoretical investigation establishes $p$WMs as a versatile platform for realizing intriguing superconducting phases including topological superconductivity (TSC), Bogoliubov Fermi surfaces (BFSs), and superconducting diode effect (SDE), within a unified microscopic framework. Employing a minimal model incorporating $p$-wave magnetic order, exchange coupling, and Zeeman fields, we perform a self-consistent mean-field analysis and uncover a rich phase diagram featuring unconventional finite-momentum Fulde-Ferrell (FF) and Larkin-Ovchinnikov (LO) superconducting phases. Remarkably, we also show that $p$WMs can undergo a transition to a TSC phase anchoring Majorana flat edge modes, a hallmark of two-dimensional TSCs, even without Rashba spin-orbit coupling and Zeeman field. Upon applying a Zeeman field, gapless FF and LO phases emerge with BFSs characterized by the appearance of finite zero-energy quasiparticle density of states. Furthermore, we demonstrate that SDE arises naturally in the asymmetric FF phase. Our analysis manifests that $p$WMs serve as a unique and novel platform to host TSC phase, gapless superconducting states, and non-reciprocal transport phenomena.

cond-mat.supr-con↗

arXiv2026

Altermagnetic phases and phase transitions in Lieb-$5$ Hubbard model

The emergence of altermagnetism, the collinear magnetic phase characterized by momentum-dependent spin-split bands but zero net magnetization, has fundamentally reshaped the classification of magnetic order. We propose an altermagnetic (AM) order in a repulsive Hubbard model on the Lieb-$5$ lattice. Considering only nearest-neighbor hoppings within the lattice, we show a phase transition from the nonmagnetic to a unique AM isolated band metal phase (AMIM), allowing clear identification of spin-split states. Additionally, the AM metallic phase (AMM) is also shown to appear as an intermediate phase during the transition from the normal metal to the AMIM in the presence of the diagonal hopping within each unit cell of the Lieb-$5$ lattice. The manifestation of distinct AM phases and the phase transitions, driven by Hubbard interaction and hopping integrals, have been explored in terms of spin-resolved band structure, spectral function, and the behavior of the AM order parameter. The stability of these AM phases against the spin-orbit coupling and temperature is also established.

cond-mat.str-el↗

arXiv2025

Spectral Bifurcation and Anomalous Supercurrent in Dissipative Topological Insulator-based Josephson Junctions

The interplay between topological protection and dissipation constitutes a critical frontier in the realization of hybrid quantum devices. Here, we investigate the transport signatures in a dissipative topological insulator-based Josephson junction, a platform that directly probes the competition between quantum coherence and loss. We model dissipation by coupling a `lossy' metallic lead to the junction, described effectively by a non-Hermitian Hamiltonian derived using the Lindblad formalism. We observe that the junction exhibits an asymmetric complex Andreev spectrum, where the imaginary energy component imposes a finite lifetime on the quasi-bound states. Furthermore, beyond specific phase intervals, the real component of the spectrum bifurcates: one branch merges with the continuum, while the other penetrates just below the superconducting gap. Crucially, the characteristic zero-energy crossing shifts away from $ϕ=π$ and acquires a non-zero imaginary component; consequently, the associated Majorana bound states acquire a finite lifetime, signaling a loss of robustness against dissipation. Finally, this spectral asymmetry drives an anomalous supercurrent, manifested as a non-vanishing current at zero phase difference. Our results reveal how dissipation fundamentally reshapes superconducting transport in topological junctions, opening new directions for dissipation-engineered quantum devices.

cond-mat.supr-con↗

arXiv2025

Thermal transport in superconductor heterostructures: some recent progress

This article reviews recent advances in low-temperature electronic thermal transport properties of thermally biased superconductor heterostructures focusing on the two-terminal transport. Since the last decade, ferromagnetism has been widely used to enhance the thermoelectricity in heterostructures based on ordinary superconductors. The possibility of getting giant thermoelectric effects with optimum thermal conductance by breaking the electron-hole symmetry of the ordinary superconductor boosted the research in this direction. Recently, attention has been paid to the role of triplet Cooper pairs that emerged in ferromagnetic junctions and the possibility of advanced applications. Other forms of magnetism, specifically antiferromagnetism and altermagnetism, have been investigated to unravel the behavior of the thermal and charge current in thermally biased junctions. In parallel to ordinary superconductors, junctions with unconventional superconductors have been explored for the same purpose. Thermal transport in superconducting bilayers has been studied using advanced materials like Dirac and topological materials, including Weyl semimetals. Significant attention has been paid to thermally biased topological Josephson junctions to explore the phase-tunable current in recent times. Weyl Josephson junctions, multi-terminal Josephson junctions, and various other multilayer junctions have also been studied to engineer large thermoelectric effects and various functionalities with potential applications in superconductor-based thermal device components.

cond-mat.supr-con↗

arXiv2025

Field-free Josephson diode effect in interacting chiral quantum dot junctions

We investigate chiral quantum dot (QD)-based Josephson junction and show the correlation-induced Josephson diode effect (JDE) in it. The presence of electron-electron interaction spontaneously creates an imbalance between up- and down-spin electrons during the non-equilibrium transport making the QD effectively magnetic. The simultaneous presence of the chirality and the interaction eventually results in the field-free JDE in our chiral QD junction. We employ the Keldysh non-equilibrium Green's function technique to study the behavior of the Josephson current (JC) and the rectification coefficient (RC) of our Josephson diode (JD). We show a sign-changing behavior of the RC with the Coulomb correlation and the lead-to-dot coupling strength and find the maximum magnitude of the RC $\sim 72\%$ for moderate interaction strength. Our proposed field-free JD based on interacting chiral QD may be a potential switching component in superconductor based devices.

cond-mat.supr-con↗

arXiv2024

Identifying Bogoliubov Fermi surfaces via thermoelectric response in a $d$-wave superconductor heterostructure

We theoretically investigate the thermoelectric response of Bogoliubov Fermi surfaces (BFSs) generated in a two dimensional unconventional $d$-wave superconductor subjected to an external in-plane Zeeman field. These BFSs exhibiting the same dimension as the underlying normal state Fermi surface are topologically protected by combinations of discrete symmetries. Utilizing the Blonder-Tinkham-Klapwijk formalism and considering normal-$d$-wave superconductor hybrid junction, we compute the thermoelectric coefficients including thermal conductance, Seebeck coefficient, figure of merit ($zT$), and examine the validation of Widemann-Franz law in the presence of both voltage and temperature bias. Importantly, as a signature of anisotropic nature of $d$-wave pairing, Andreev bound states (ABSs) formed at the normal-superconductor interface play a significant role in the thermoelectric response. In the presence of ABSs, we observe a substantial enhancement in Seebeck coefficient ($\sim 200\,μ$V/K) and $zT$ ($\sim 3.5$) due to the generation of the BFSs and thus making such setup a potential candidate for device applications. Finally, we strengthen our continuum model results by computing the thermoelectric coefficients based on a lattice-regularized version of our continuum model.

cond-mat.supr-con↗

arXiv2024

Quasiparticles-mediated thermal diode effect in Weyl Josephson junctions

We theoretically show quasiparticles-driven thermal diode effect (TDE) in an inversion symmetry-broken (ISB) Weyl superconductor (WSC)-Weyl semimetal (WSM)-WSC Josephson junction. A Zeeman field perpendicular to the WSM region of the thermally-biased Weyl Josephson junction (WJJ) induces an asymmetry between the forward and reverse thermal currents, which is responsible for the TDE. Most interestingly, we show that the sign and magnitude of the thermal diode rectification coefficient is highly tunable by the superconducting phase difference and external Zeeman field, and also strongly depends on the junction length. The tunability of the rectification, particularly, the sign changing behavior associated with higher rectification enhances the potential of our WJJ thermal diode to use as functional switching components in thermal devices.

cond-mat.supr-con↗

arXiv2024

Fermi arcs mediated transport in inversion symmetry-broken Weyl semimetal nanowire and its hybrid junctions

The emergence of gapless surface states, known as Fermi arcs (FAs), is one of the unique properties of the novel topological Weyl semimetal (WSM). However, extracting the signatures of FAs from the bulk states has always been a challenge as both of them are gapless in nature and connected to each other. We capture the signatures of FAs via transport in an inversion symmetry (IS)-broken WSM. We study the band structure and the properties of FAs like shape, spin polarization considering slab and nanowire (NW) geometry, and then compute the two-terminal conductance in WSM NW in terms of the scattering coefficients within the Landauer formalism. We find the FA-mediated conductance to be quantized in units of $2e^2/h$. We extend our study to the transport in WSM/Weyl superconductor (WSC) NW hybrid junction using the Blonder-Tinkham-Klapwijk (BTK) formalism. We show that due to the intricate spin textures, the signatures of the FAs can be captured via Andreev reflection process. We also show that our results of conductance are robust against delta-correlated quenched disorder and thus enhancing the experimental feasibility.

cond-mat.mes-hall↗

arXiv2024

Transport signatures of Bogoliubov Fermi surfaces in normal metal/time-reversal symmetry broken $d$-wave superconductor junctions

In recent times, Bogoliubov Fermi surfaces (BFSs) in superconductors (SCs) have drawn significant attention due to a substantial population of Bogoliubov quasiparticles (BQPs) together with Cooper pairs (CPs) in them. The BQPs as zero energy excitations give rise to captivating and intricate charge dynamics within the BFSs. In this theoretical study, we propose to reveal the unique signatures of the topologically protected BFSs in bulk $d$-wave SCs using normal metal/time-reversal symmetry (TRS) broken $d$-wave SC hybrid setup, in terms of the differential conductance and Fano factor (FF). Orientation of crystal $a$ axis with respect to junction normal, quantified by the parameter $α$, is crucial for transport properties in these hybrid devices. For $α=0$, an enhancement in zero-bias conductance (ZBC) can be identified as a key signature of BFSs. However, for $α\ne0$, this feature does not replicate due to the presence of the localized Andreev bound state (ABS) at the interface. The interplay of ABS and BFSs gives rise to an anomalous behavior in ZBC compared to the $α=0$ case. This behavior remains qualitatively similar even at finite temperatures. Finally, we explain this anomalous behavior by analyzing the effective charge of the carriers in terms of the FF. The simplicity of our setup based on $d$-wave SC makes our proposal persuasive.

cond-mat.supr-con↗

arXiv2024

Gate-tunable Josephson diode effect in Rashba spin-orbit coupled quantum dot junctions

We theoretically explore Josephson diode effect (JDE) in superconductor/quantum dot (QD)/superconductor junction in the presence of a magnetic field and Rashba spin-orbit interaction (RSOI). We calculate the Josephson current in our QD junction using Keldysh non-equilibrium Green's function technique. We show that JDE is induced in our chiral QD junction with large rectification coefficient (RC) in the presence of RSOI and external magnetic field simultaneously. Interestingly, the sign and magnitude of the RC are highly controllable by the magnetic field and RSOI. For realistic RSOI strength in the presence of magnetic field and chirality, the RC can be tuned to be as high as $70\%$ by an external gate potential, indicating a giant JDE in our QD junction. Our proposed QD-based Josephson diode (JD) may serve as a potential superconducting device component.

cond-mat.supr-con↗

arXiv2024

Nonlocality of Majorana bound states revealed by electron waiting times in a topological Andreev interferometer

The analysis of waiting times of electron transfers has recently become experimentally accessible owing to advances in noninvasive probes working in the short-time regime. We study electron waiting times in a topological Andreev interferometer: a superconducting loop with controllable phase difference connected to a quantum spin Hall edge, where the edge state helicity enables the transfer of electrons and holes into separate leads, with transmission controlled by the loop's phase difference $ϕ$. This setup features gapless Majorana bound states at $ϕ=π$. The waiting times for electron transfers across the junction are sensitive to the presence of the gapless states, but are uncorrelated for all $ϕ$. By contrast, at $ϕ=π$ the waiting times of Andreev-scattered holes show a strong correlation and the crossed (hole-electron) distributions feature a unique behavior. Both effects exclusively result from the nonlocal properties of Majorana bound states. Consequently, electron waiting times and their correlations could circumvent some of the challenges for detecting topological superconductivity and Majorana states beyond conductance signatures.

cond-mat.supr-con↗

arXiv2023

Phase-dependent charge and heat current in thermally biased short Josephson junctions formed at helical edge states

We explore the phase-dependent charge and heat current in the short Josephson junctions with two normal metal regions attached at opposite ends, formed at helical edge states of two-dimensional topological insulators (TIs). For all finite phases, an asymmetry appears around the zero energy in the transmission spectra except for $ϕ\!=\!nϕ_0$, where $n$ is a half-integer and $ϕ_0$ ($=2π$) is the flux quantum. The phase-induced asymmetry plays a key role in inducing charge and heat current through the thermally biased junction. However, the current amplitudes are sensitive to the size of the junction. We show that in the short Josephson junction when subject to a temperature gradient, the charge current shows an odd-symmetry in phase. It indicates that the phase-tunable asymmetry around the zero-energy is not sufficient to induce a dissipative thermoelectric current in the junction. This is in contrast to the behavior of long Josephson junction as shown in the literature. The phase-tunable heat currents are obtained with amplitudes set by the phase difference, base temperature, and system size.

cond-mat.supr-con↗

arXiv2023

Tunable phase transitions in half-Heusler TbPtBi compound

We report various phase transitions in half-Heusler TbPtBi compound using Density Functional Theory (DFT). Specifically, inclusion of spin-orbit coupling (SOC) leads to band inversion resulting in transition from the metallic to the topological semimetallic phase. However, in presence of SOC, there is a phase transition from the topological semimetal to the trivial semimetal when the material is subjected to compressive strain ($\lt -7\%$). Subsequently, under further increase of compressive strain ($\ge -7\%$), we find an opening of a direct band gap at the $Γ$ point, driving the system from the trivial semimetallic to the semiconducting state with changes in the sequence of bands. In the absence of SOC, only transition from the metallic to the semiconducting phase is noticed. Under tensile strain, the TbPtBi compound maintains its phase as in the unstrained condition but with an increase in the hole pocket at the Fermi level, both in the absence and presence of SOC. These tunable phase transitions (especially as a fraction of strain) make this compound very promising for application in various quantum devices such as highly sensitive strain gauges.

cond-mat.mtrl-sci↗