arXiv subjects

K. Mukherjee

Publications and source records attributed to K. Mukherjee.

At least 19 recordsLinked to original sources

arXiv2026

Unveiling the Superconducting Ground State of Heusler alloy Pd2ZrIn via muon spin relaxation and rotation measurement

Full Heusler alloys XInPd2 (X= Zr, Hf and Ti) have recently attracted significant attention owing to their symmetry-driven electronic structure and also due to the interplay between disorder and emergent ground states. Within this family, Pd2ZrIn serves as a unique platform to study the effect of disorder on superconducting pairing. This alloy crystallizes in a cubic L21 structure with significant B2-type antisite disorder. Electrical resistivity and magnetic susceptibility studies confirm bulk type-II superconductivity with a transition temperature TC ~ 2.2 K. Zero-field {\mu}SR results reveal no evidence of spontaneous internal magnetic fields below TC, confirming the preservation of time-reversal symmetry. Transverse-field {\mu}SR spectra show the formation of a vortex lattice, consistent with type-II superconductivity, and the superfluid density is well described by a fully gapped, nodeless s-wave state with superconducting gap {\Delta} (0) ~ 0.33 \pm 0.01 meV. Furthermore, the estimated ratio of transition temperature and Fermi temperature (TC/TF) indicates that this alloy lies within the conventional superconducting regime on the Uemura plot. These results establish Pd2ZrIn as a weakly coupled, dirty-limit, type-II superconductor; with a fully gapped, nodeless order parameter and preserved time-reversal symmetry.

cond-mat.supr-con↗

arXiv2026

Unusual magnetic and charge transport properties in In-Substituted Half-Metallic Kagome Ferromagnet Co3Sn2S2

The kagome ferromagnet Co3Sn2S2 has been studied extensively for its unusual topology of electronic bands, origin of ferromagnetism and strong coupling between magnetism and charge transport. To understand the role of nonmagnetic element Sn, we have investigated magnetic, transport, and electronic structure of the isostructural compound Co3SnInS2, where all the Sn (divalent) atoms in the Co3Sn Kagome layer are replaced by In (trivalent) atoms. We find long-range ferromagnetic order is nearly quenched in Co3SnInS2. The system exhibits predominantly antiferromagnetic correlations with only a very small net magnetic moment and turns ferromagnetic in the presence of an external magnetic field. Transport measurements show a semiconducting behaviour at low temperatures. Magnetoresistance shows a nonmonotonic field dependence, changing from negative to positive with increasing magnetic field. An anomalous Hall effect is observed, but its magnitude is significantly reduced compared to Co3Sn2S2 where the topological character of the Fermi surface plays a dominant role. These results indicate that substitution of Sn by In in the Co3Sn plane not only suppresses the topological electronic features of the transport electrons but drives the system away from the ferromagnetic Half-metallicity to an almost nonmagnetic semiconducting state with unusual paramagnetic response. Electronic structure calculations are consistent with some of these observations.

cond-mat.mtrl-sci↗

arXiv2024

Generation of wave turbulence in dipolar gases driven across their phase transitions

Ultracold quantum gases with long-range anisotropic interactions host novel exotic phases of matter, such as supersolids, exhibiting both rigid and superfluid characteristics. The impact of this interplay on the out-of-equilibrium dynamics of dipolar gases, and in particular its connection with universal turbulent behavior, remains highly unexplored. Here, upon considering a dipolar Bose-Einstein condensate of dysprosium atoms being dynamically driven across the supersolid-superfluid phase transition and vice versa, we unveil the emergence of a robust nonequilibrium quasi-steady state. This state displays self-similar momentum distributions exhibiting algebraic decay at large momenta, with scaling exponents supporting the existence of wave turbulence. We demonstrate that supersolidity sustaining higher-lying momenta, associated with the roton minimum, promotes the development of turbulence. Our results provide a stepping stone toward unraveling and exploiting turbulent and self-similar behavior in anisotropically long-range interacting quantum gases amenable in current experiments.

cond-mat.quant-gas↗

arXiv2024

Selective Rotation and Attractive Persistent Currents in Anti-Dipolar Ring Supersolids

A repulsively interacting Bose-Einstein condensate on a ring is well known to show persistent currents. For attractive interactions, however, a bound state may form that renders the rotation classical. Here we show that in a multiply-connected confinement, the strong in-plane attraction of an {\it anti-dipolar }condensate can form stacks of ring-shaped droplets which may coherently overlap to form a supersolid along the azimuthal symmetry axis of the system. Intriguingly, the functional behavior of the energy-angular momentum dispersion of the anti-dipolar ring condensate differs from that of a usual repulsive superfluid. The periodic maxima between persistent flow and the non-rotating ground state flatten significantly and the typical pronounced cusps in the energy dispersion also occur in the rotationally symmetric supersolid state. A weak link results in the reduction of this minimum, shifting it to smaller angular momenta. With an asymmetric link potential one can selectively induce superfluid and rigid-body rotation in different layers within the same system. This intriguing setup offers new perspectives for atomtronics applications.

cond-mat.quant-gas↗

arXiv2024

Tunneling dynamics of $^{164}$Dy supersolids and droplets

The tunneling dynamics of a magnetic $^{164}$Dy quantum gas in an elongated or pancake skewed double-well trap is investigated with a time-dependent extended Gross-Pitaevskii approach. Upon lifting the energy offset, different tunneling regimes can be identified. In the elongated trap and for sufficiently large offset, the different configurations exhibit collective macroscopic tunneling. For smaller offset, partial reflection from and transmission through the barrier lead to density accumulation in both wells, and eventually to tunneling-locking. One can also reach the macroscopic self-trapping regime for increasing relative dipolar interaction strength, while tunneling vanishes for large barrier heights. A richer dynamical behavior is observed for the pancake-like trap. For instance, the supersolid maintains its shape, while the superfluid density gets distorted signifying the emergence of peculiar excitation patterns in the macroscopic tunneling regime. The findings reported here may offer new ways to probe distinctive dynamical features in the supersolid and droplet regimes.

cond-mat.quant-gas↗

arXiv2023

Excitons guided by polaritons

We show that an exciton on a discrete chain of sites can be guided by effective measurements induced by an ambient, non-equilibrium medium that is synchronised to the exciton transport. For experimental verification, we propose a hybrid cold atom platform, carrying the exciton as electronic excitation on a chain of atoms, which are surrounded by a slow light medium supporting polaritons. The chain is coupled to the medium through long-range Rydberg interactions. Despite the guiding mechanism being incoherent, the exciton pulse can be coherently transported with high fidelity. The implementation requires careful alignment of chain and medium but then no further time-dependent control. Our concept can be ported to other exciton and polariton carrying media or devices, and will enable switches and waveguides operating with the two quasi particles involved, as we demonstrate.

quant-ph↗

arXiv2022

Classical linear chain behavior from dipolar droplets to supersolids

We investigate the classicality of linear dipolar droplet arrays through a normal mode analysis of the dynamical properties in comparison to the supersolid regime. The vibrational patterns of isolated-droplet crystals that time-evolve after a small initial kick closely follow the properties of a linear droplet chain. For larger kick velocities, however, droplets may coalesce and separate again, showing distinct deviations from classicality. In the supersolid regime the normal modes are eliminated by a counter-flow of mass between the droplets, signaled by a reduction of the center-of-mass motion.

cond-mat.quant-gas↗

arXiv2022

Impact of Doping and Geometry on Breakdown Voltage of Semi-Vertical GaN-on-Si MOS Capacitors

For the development of reliable vertical GaN transistors, a detailed analysis of the robustness of the gate stack is necessary, as a function of the process parameters and material properties. To this aim, we report a detailed analysis of breakdown performance of planar GaN-on-Si MOS capacitors. The analysis is carried out on capacitors processed on different GaN bulk doping (6E18 Si/cc, 6E17 Si/cc and 2.5E18 Mg/cc, p-type), different structures (planar, trench-like) and different geometries (area, perimeter and shape). We demonstrate that (i) capacitors on p-GaN have better breakdown performance; (ii) the presence of a trench structure significantly reduces breakdown capabilities; (iii) breakdown voltage is dependent on area, with a decreasing robustness for increasing dimensions; (iv) breakdown voltage is independent of shape (rectangular, circular). TCAD simulations, in agreement with the measurements, illustrate the electric field distribution near breakdown and clarify the results obtained experimentally.

physics.app-ph↗

arXiv2022

Van Vleck paramagnetism and enhancement of effective moment with magnetic field in rare earth orthovanadate EuVO4

The 4f^6 systems were hypothesized to possess non-magnetic (J = 0) ground state. However, all such systems have distinctly shown the presence of non-zero effective moment. In this context, a rare earth orthovanadate EuVO4, which in spite of having J = 0 ground state, possess non-zero magnetic moment. Our studies reveal three different regions in this compound, boundaries of which are demarcated from susceptibility data. The high temperature susceptibility exhibits linear dependence on temperature which arises due to tetragonal crystal field, followed by a temperature independent plateau like region, ascribed to Van Vleck paramagnetism. At low temperatures, Curie-Weiss like behaviour is observed, which arise due to magnetic Eu2+ moments and results in non-zero effective moment. Our analysis reveals that the separation ({\lambda}) between the J = 0 and J = 1 states decreases on increasing the external magnetic field which leads to an enhanced effective moment at higher fields.

cond-mat.str-el↗

arXiv2022

Possible realization of three-dimensional quantum spin liquid behavior in HoVO4

The study of geometrically frustrated magnetic systems with unusual crystal field ground states offers a possibility of realizing the new aspects of physics of disordered systems. In this study, we report our results of structural, magnetic susceptibility, heat capacity measurements, along with density functional theory calculations on HoVO4; a compound in which the presence of a distorted kind of HoO8 polyhedral leads to multiple magnetic interaction paths. The observed broad maximum below 10 K in the temperature response of DC susceptibility curves implies the presence of short-range correlations. AC susceptibility rules out the possibility of any kind of spin freezing. Temperature dependent heat capacity measurement at zero field indicate towards the absence of long-range ordering, along with the presence of a broad maximum centered around 14 K. The residual heat capacity exhibits a characteristic power-law (T{\alpha}) behavior with the exponent {\alpha} nearly equal to 2, which is analogous to that observed for other 3D quantum spin liquid systems. The density functional theory calculations signify the presence of dominant second and third nearest neighbor interactions, which in turn lead to magnetic frustration in our system. Our investigations suggest that HoVO4 can be a candidate for realizing a 3D quantum spin liquid state.

cond-mat.str-el↗

arXiv2022

Unravelling the signatures of effective spin 1/2 moments in CeVO4: Magnetization and Heat Capacity study

The realization of an effective spin (Jeff) 1/2 state at low temperatures offers a platform to study the enthralling physics behind the disordered states in certain systems. Here, we report the signatures of magnetic ground state associated with Jeff = 1/2 in CeVO4. Our studies confirm the absence of any ordering or freezing down to 1.8 K. In the low temperature region, the Curie-Weiss fit of the inverse DC susceptibility indicate towards the presence of antiferromagnetic correlations among the Ce3+ spins. The calculated value of effective moment (~1.16 {\mu}_B) corresponds to J = 1/2 with gJ ~ 1.20. Further, the field dependent magnetization curve at 2 K follows a behaviour corresponding to J = 1/2 Brillouin function with gJ ~ 1.13. Magnetic field dependent heat capacity fits very well with two-level Schottky scheme. Our investigations suggest that CeVO4 can be a promising candidate to realise Jeff = 1/2 properties among 3D spin systems

cond-mat.str-el↗

arXiv2022

Emergence of low temperature glassy dynamics in Ru substituted non magnetic insulator CaHfO3

Non magnetic insulators/semiconductors with induced magnetism introduced via transition metal substitution are one of the promising materials in the field of spintronic, magnetoelectronics and magneto optical devices. In this context, here, we focus on magnetism induced in a non magnetic insulator CaHfO3, by the substitution of 4d element Ru, at Hf site. Structural investigations indicate that substitution of Ru4+ (up to 50%) does not affect the original crystal structure of the parent compound. Magnetic studies divulge a crossover from a diamagnetic to paramagnetic state with 20% Ru substitution. Further replacement of Hf results in a glassy magnetic state in CaHf1-xRuxO3 (0.3 < x < 0.5). The nature of the low temperature glassiness (below 20 K) in these compositions is confirmed through Vogel Fulcher and Power law, along with, magnetic memory effect and relaxation dynamics. The observed glassiness is explained through the phenomenological hierarchical model. Our studies indicate that the presence of competing short range interactions among randomly arranged Ru cations in non magnetic insulator CaHfO3 are responsible for the observed low temperature magnetic state in this series with compositions > 0.25.

cond-mat.str-el↗

arXiv2022

Melting of spin ice state and development of fifth order susceptibility with magnetic field in pyrochlore Tb2Sn2O7

Pyrochlores offer an ideal playground to investigate the magnetic ground state of frustrated magnetic systems. In this class of materials, competition between various magnetic interactions remains frustrated and prevents an ordered magnetic state at low temperatures. Tb2Sn2O7 has recently attracted significant attention due to its ordered spin-ice state. Additionally, in such systems, application of external magnetic field might result in exotic magnetic states. Our current investigation on Tb2Sn2O7 reveal the presence of a new phase associated with fifth order susceptibility at low temperatures and high magnetic fields. In this compound, at zero fields, for a stabilized spin-ice state, the singlet-singlet state separated by {\delta} play an imperative role. Under magnetic fields, {\delta} increases and the Zeeman energy associated with the magnetic anisotropy is believed to get enhanced; which can be the key ingredient for evolution of higher-order moments, above 10 kOe, in this compound.

cond-mat.str-el↗

arXiv2022

Study and characterization of GaN MOS capacitors: planar versus trench topographies

Developing high quality GaN/dielectric interfaces is a fundamental step for manufacturing GaN vertical power transistors. In this paper, we quantitatively investigate the effect of planar etching treatment and trench formation on the performance of GaN-based MOS (metal oxide semiconductor) stacks. The results demonstrate that (i) blanket etching the GaN surface does not degrade the robustness of the deposited dielectric layer; (ii) the addition of the trench etch, while improving reproducibility, results in a decrease of breakdown performance compared to the planar structures. (iii) for the trench structures, the voltage for a 10 years lifetime is still above 20 V, indicating a good robustness. (iv) To review the trapping performance across the metal-dielectric-GaN stack, forward-reverse capacitance-voltage measurements with and without stress and photo-assistance are performed. Overall, as-grown planar capacitors devoid of prior etching steps show lowest trapping, while trench capacitors have higher interface trapping, and bulk trapping comparable to the blanket etched capacitors. (v) The nanostructure of the GaN/dielectric interface was characterized by high resolution scanning transmission electron microscopy (HR-STEM). An increased roughness of 2-3 monolayers at the GaN surface was observed after blanket etching, which was correlated to the higher density of interface traps. The results presented in this paper give fundamental insight on how the etch and trench processing affects the trapping and robustness of trench-gate GaN-MOSFETs, and provide guidance for the optimization of device performance.

physics.app-ph↗

arXiv2022

Control of $^{164}$Dy Bose-Einstein condensate phases and dynamics with dipolar anisotropy

We investigate the quench dynamics of quasi-one and two dimensional dipolar Bose-Einstein condensates (dBEC) of $^{164}$Dy atoms under the influence of a fast rotating magnetic field. The magnetic field thus controls both the magnitude and sign of the dipolar potential. We account for quantum fluctuations, critical to formation of exotic quantum droplet and supersolid phases in the extended Gross-Pitaevskii formalism, which includes the so-called Lee-Huang-Yang (LHY) correction. An analytical variational ansatz allows us to obtain the phase diagrams of the superfluid and droplet phases. The crossover from the superfluid to the supersolid phase and to single and droplet arrays is probed with particle number and dipolar interaction. The dipolar strength is tuned by rotating the magnetic field with subsequent effects on phase boundaries. Following interaction quenches across the aforementioned phases, we monitor the dynamical formation of supersolid clusters or droplet lattices. We include losses due to three-body recombination over the crossover regime, where the three-body recombination rate coefficient scales with the fourth power of the scattering length ($a_s$) or the dipole length ($a_{dd}$). For fixed values of the dimensionless parameter, $\epsilon_{dd} = a_{dd}/a_s$, tuning the dipolar anisotropy leads to an enhancement of the droplet lifetimes.

cond-mat.quant-gas↗

arXiv2022

Atomic disorder and Berry phase driven anomalous Hall effect in Co2FeAl Heusler compound

Co2-based Heusler compounds are the promising materials for the spintronics application due to their high Curie temperature, large spin-polarization, large magnetization density, and exotic transport properties. In the present manuscript, we report the anomalous Hall effect (AHE) in a polycrystalline Co2FeAl Heusler compound using combined experimental and theoretical studies. The Rietveld analysis of high-resolution synchrotron x-ray diffraction data reveals a large degree (~50 %) of antisite disorder between Fe and Al atoms. The analysis of anomalous transport data provides the experimental anomalous Hall conductivity (AHC) about 227 S/cm at 2 K with an intrinsic contribution of 155 S/cm, which has nearly constant variation with temperature. The detailed scaling analysis of anomalous Hall resistivity suggests that the AHE in Co2FeAl is governed by the Berry phase driven intrinsic mechanism. Our theoretical calculations reveal that the disorder present in Co2FeAl compound enhances the Berry curvature induced intrinsic AHC.

cond-mat.mtrl-sci↗

arXiv2021

Entropic topography associated with field-induced quantum criticality in a magnetic insulator DyVO4

Exploration of low temperature phase transitions associated with quantum critical point is one of the most mystifying fields of research which is under intensive focus in recent times. In this work, through comprehensive experimental evidences, we report the possibility of achieving quantum criticality in the neighborhood of a magnetic field-tuned tricritical point separating paramagnetic, antiferromagnetic and metamagnetic phases in a magnetic insulator, DyVO4. Magnetic susceptibility and heat capacity indicate to the presence of a long-range second order antiferromagnetic transition at TN ~ 3.2 K. Field variation of Magnetic susceptibility and heat capacity, along with differential magnetic susceptibility and DC field dependent AC susceptibility gives evidence of the modification of the antiferromagnetic structure below the tricritical point; implying the presence of a field-induced first order metamagnetic transition which persists down to 1.8 K. Further, the magnetic field dependence of the thermodynamic quantity -dM/dT, which is related to magnetic Gruneisen parameter, approaches a minimum, followed by a crossover near 5 kOe to a maximum; along with a hyperbolic divergence in temperature response of dM/dT in the critical field regime. Temperature response of heat capacity at 5 kOe also shows a deviation from the conventional behavior. Entropic topography phase diagram allows tracking of the variation of the entropy, which indicates towards the emergence of the peak at quantum critical point into a V-shaped region at high temperatures. Our studies yield an inimitable phase diagram describing a tricritical point at which the second-order antiferromagnetic phase line terminates followed by a first order line of metamagnetic transition, as the temperature is lowered, leading to metamagnetic quantum critical end point.

cond-mat.str-el↗

arXiv2021

Large magnetodielectric coupling in the vicinity of metamagnetic transition in $6H-$perovskite Ba$_3$GdRu$_2$O$_9$

The 6H-perovskites Ba$_3$RRu$_2$O$_9$ (R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of $4d - 4f$ magnetic interactions. Here, we have reported a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba$_3$GdRu$_2$O$_9$. The signature of long-range antiferromagnetic (AFM) ordering $\sim$ 14.8 K ($T_N$) is evident from the magnetization and heat capacity studies. The $T_N$ shifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magnetization at 1.8 K shows three metamagnetic transitions with the opening of small hysteresis in different regions. A new transition at $T_1$ emerges after the onset of the first metamagnetic transition. Complex magnetic behavior is observed in different magnetic field regions whereas these field regions themselves vary with the temperature. Dielectric response recorded at zero and 80 kOe field exhibits the development of MD coupling well above $T_N$. The MD coupling ($\sim$ 4.5 \% at 10 K) is enhanced by 25 \% as compared to the Dy counterpart. Effect of complex magnetic behavior is also conveyed in the MD results where the maximum value of MD coupling is observed in the vicinity of 10 K (onset of $T_1$) and near the second metamagnetic transition. Our investigation suggests that both Gd and Ru moments align simultaneously at $T_N$. Short-range magnetic correlations are possibly responsible for MD coupling above $T_N$.

cond-mat.str-el↗