arXiv subjects

Pritam Deb

Publications and source records attributed to Pritam Deb.

11 recordsLinked to original sources

arXiv2025

Strong altermagnetism and topological features in a two-dimensional van der Waals heterostructure via broken time reversal symmetry

The advent of altermagnetism, a new phase of magnetism, has garnered significant interest due to its extraordinary spin-polarized electronic bands despite zero net magnetization. Such spin-symmetry-guided robust non-relativistic alternating spin splitting in a compensated collinear magnet presents a novel platform for magnetotransport and nontrivial topology. Predominantly, altermagnetic behavior is observed in bulk magnetic materials upon incorporating external perturbations. However, van der Waals heterostructures can offer exceptional flexibility in tailoring their various emerging properties without the need for external perturbations in the two-dimensional regime. Here, an unconventional time reversal symmetry breaking with sizeable spin splitting via broken space-spin symmetry (\textit{P$\mathcal{T}$}) has been demonstrated in an antiferromagnet/nonmagnet vdW heterostructure. The lifted Kramer's degeneracy alongwith spin-orbit interactions result in non-zero Berry curvature, contributing to the outstanding magnetotransport with a large value of anomalous Hall conductivity ($\sim 732.9\ {\mathit{\Omega}}^{-1}{cm}^{-1}$). The presence of relativistic spin-orbit interactions in addition to predominant non-relativistic effects governed spin-momentum locking with a weak out-of-plane Dzyaloshinskii-Moriya interaction, which induces small spin canting. Further, the lowest magnetic anisotropy energy confirms collinear antiferromagnetic ground state. In particular, a nontrivial topology is observed along the surface [001], which is confirmed by the non-zero Chern number. This study provides a novel approach to realize strong altermagnetism in broken space-spin symmetry systems and fosters emergent transport behaviors.

cond-mat.mtrl-sci↗

arXiv2024

Room-temperature tunable tunneling magnetoresistance in Fe3GaTe2/WSe2/Fe3GaTe2 van der Waals heterostructures

The exceptional properties of two-dimensional (2D) magnet materials present a novel approach to fabricate functional magnetic tunnel junctions (MTJ) by constructing full van der Waals (vdW) heterostructures with atomically sharp and clean interfaces. The exploration of vdW MTJ devices with high working temperature and adjustable functionalities holds great potential for advancing the application of 2D materials in magnetic sensing and data storage. Here, we report the observation of highly tunable room-temperature tunneling magnetoresistance through electronic means in a full vdW Fe3GaTe2/WSe2/Fe3GaTe2 MTJ. The spin valve effect of the MTJ can be detected even with the current below 1 nA, both at low and room temperatures, yielding a tunneling magnetoresistance (TMR) of 340% at 2 K and 50% at 300 K, respectively. Importantly, the magnitude and sign of TMR can be modulated by a DC bias current, even at room temperature, a capability that was previously unrealized in full vdW MTJs. This tunable TMR arises from the contribution of energy-dependent localized spin states in the metallic ferromagnet Fe3GaTe2 during tunnel transport when a finite electrical bias is applied. Our work offers a new perspective for designing and exploring room-temperature tunable spintronic devices based on vdW magnet heterostructures.

cond-mat.mes-hall↗

arXiv2019

Magnetic memory effect in ensembles of interacting anisotropic magnetic nanoparticles

We explore the influence of demagnetization interaction on magnetic memory effect by varying organization geometry of anisotropic ZnFe$_2$O$_4$ nanoparticles in an ensemble. The static and dynamic behaviour of two differently organized ensembles, compact ensemble (CE) and hollow core ensemble (HCE), are extensively studied by both dc and ac susceptibility, magnetic memory effect and spin relaxation. The frequency-dependence peak shifting of freezing temperature in both the systems is analyzed properly with the help of two dynamic scaling models: Vogel-Fulcher law and power law. Presence of cluster spin-glass phase is reflected from Vogel-Fulcher temperature $T_0$ $\simeq$ 142.58 K for CE, $\simeq$ 97 K for HCE and characteristic time constant $\tau_0$ $\simeq$ $8.85\times10^{-9}$ s for CE, $\simeq$ $3.8\times10^{-10}$ s for HCE; along with $\delta$T$_{Th}$ $\sim$ 0.1 for CE and 0.2 for HCE. The power law fitting with dynamic exponent $zv'$ = 6.2 $\pm$ 1.1 for CE, 6.3 $\pm$ 0.5 for HCE and single spin flip $\tau^*$ $\simeq$ $7.7\times10^{-11}$ s for CE, $\simeq$ $1.3\times10^{-10}$ s for HCE provide firm confirmation of cluster spin-glass phase. The progressive spin freezing across multiple metastable states with prominent memory effects is reflected in both the systems via nonequilibrium dynamics study. The hollow core geometry with anisotropic nanoparticles on surface with closer proximity leads to complex anisotropy energy landscape with enhanced demagnetizing field resulting highly frustrated surface spins. As a consequence, more prominent magnetic memory effect is observed in HCE with higher activation energy, reduced blocking temperature and enhanced coercivity than that of CE.

cond-mat.mtrl-sci↗

arXiv2019

Proximity effects in Graphene and Ferromagnetic CrBr3 van der Waals Heterostructure

We report on first-principle calculations on magnetic proximity effect in a van der Waals heterostructure formed by a graphene monolayer induced by its interaction with a two-dimensional (2D) ferromagnet (chromium tribromide, CrBr3). We observe that the magnetic proximity effect arising from the spin-dependent interlayer coupling depends sensitively on the interlayer electronic configuration. The proximity effect results in spin polarization of graphene orbital by up to 63.6 %, together with a miniband splitting band gap of about 73.4 meV and 8% enhancement in magnetic moment (3.47${\mu}$B/cell) in heterostructure. The position of the Fermi level in the Dirac cone is shown to depend strongly on the graphene-CrBr3 interlayer separation of 3.77 Angstrom. Consequently, we also show that a perpendicular electric field can be used to control the miniband spin splitting and transmission spectrum. Also, the interfacial polarization effect due to the existence of two different constituents reinforces the conductivity via electrostatic screening in the heterolayer. These findings point toward potential nanoscale devices where the electric field driven magnetic proximity effect can lead to unique spin controllability and possible engineering of spin gating.

cond-mat.mes-hall↗

arXiv2019

Electronic structure and Magneto-transport in MoS$_2$/Phosphorene van der Waals heterostructure

The time-dependent spin current mediated spin transfer torque behaviour has been investigated via scattering formalism within density functional theory framework supported by Green's function. Quantum magnetotransport characteristics have been revealed in a model semiconducting MoS$_2$/phosphorene van der Waals heterostructure. The dynamics of spin current channelized heterolayer transport has been studied with rotational variation in magnetization angle. It is observed that the time-dependent spin transport torque remains invariant irrespective of magnetization angle direction. The polarized spin-current is persistent with the external magnetic field for potential applicability towards spintronics.

cond-mat.mes-hall↗

arXiv2019

Two Dimensional heterostructure and its application in efficient quantum energy storage

Portable miniaturized energy storage micro-supercapacitor has engrossed significant attention due to its power source and energy storage capacity, replacing batteries in ultra-small electronic devices. Fabrication with porous and 2D graphitic nanomaterials with high conductivity and surface area signify high performance of micro-supercapacitor. In order to satisfy the fast-growing energy demands for the next-generation, we report performance and design of a 2D heterostructure of EDLC (g-C$_3$N$_4$) & pseudocapacitive (FeNi$_3$) resulting low ionic diffusion path and prominent charge storage based on their synergic functionalities. This heterostructure system shows an enhanced quantum capacitance (38% enhancement) due to delocalized states near Fermi level. Having achieved the areal capacitance of 19.21 mFcm$^{-2}$, capacitive retention (94%), enhanced power density (17 fold) having ultrahigh energy density of 0.30 Wh.cm$^{-3}$ and stability of the material even without any obvious degradation after 1000 cycles, this smart heterostructure acts as a new platform for designing high-performance in-plane micro-supercapacitor.

physics.app-ph↗

arXiv2018

Dynamic patterning and texture evolution of microbubbles in non-Newtonian immobile droplet

The dynamical perspectives of bubble in a liquid droplet on smooth solid substrate can be revealed by investigating interfacial self-assembly phenomena. Moreover, the complexity in such system can be scaled down into a transparent immobile non-Newtonian droplet. Here we present the dynamical approaches of internal microbubbles through coalescence and implosion near the edge of the droplet. The aggregation density of microbubbles near the rim is greater than the central region corresponding to the dynamical behaviour of the droplet marked with capillary flow along the triple phase contact line. We have also numerically analysed the occurrence of aggregation density of internal microbubbles near the edge by implementing boundary integral method. Our numerical results show good agreement with the experimental findings until the aggregation density have occurred near the edge of the droplet. This understanding ascribes distinctive skew exponential power law characteristics through coalescence and implosion.

cond-mat.soft↗

arXiv2018

Renormalization group analysis of weakly interacting van der Waals Fermi system

Weak-coupling phenomena of the two-dimensional Hubbard model is gaining momentum as a new interesting research field due to its extraordinarily rich behavior as a function of the carrier density and model parameters. Salmhofer [{\it Commun. Math. Phys}. \textbf{194}, 249 (1998);{\it Phys. Rev. Lett}. {\bf 87}, 187004 (2001)] developed a new renormalization-group method for interacting Fermi systems and Metzner [{\it Phys. Rev. B} {\bf 61}, 7364 (2000);{\it Phys. Rev. Lett}. {\bf 85}, 5162 (2000)] implemented this renormalization group analysis of the two-dimensional Hubbard model. In this work, we demonstrate the spin-wave dependent susceptibility behavior of model graphene-phosphorene van der Waals heterostructure in the framework of renormalization group approach. We implement signlet vertex response function for the weakly interacting van der Waals Fermi system with nearest-neighbor hopping amplitudes. This analytical approach is further correlated with {\it ab initio} simulation results and extended for spin-wave dependent susceptibility behavior with possible experimental protocols. We present the resulting compressibility and phase diagram in the vicinity of half-filling, and also results for the density dependence of the critical energy scale.

cond-mat.mes-hall↗

arXiv2018

PAW mediated ab initio simulations on linear response phonon dynamics of anisotropic black phosphorous monolayer for thermoelectric applications

The first order standard perturbation theory combined with ab initio projector augmented wave operator challenges the realization of the standard Sternheimer equation with linear computational efficiency. This efficiency motivates us to describe the electron-phonon interaction in two-dimensional (2D) black phosphorous monolayer using generalized density functional perturbation theory (DFPT) with Boltzmann transport theory (BTE). Subsequently, linear response phonon dynamic behaviour in terms of conductivities, seebeck coefficients and transport properties are focused for its thermoelectric application. The analysis reveals the crystal orientation dependence via structural anisotropy and the density of states of the monolayer structure. Momentum dependent phonon population dynamics along with the phonon linewidth are efficient in terms of reciprocal space electronic states. The optimized values of thermal conductivities of electrons and Seebeck coefficients act as driving force to modulate thermoelectric effects. Figure of merit is calculated to be 0.074 at 300 K and 0.152 at 500 K of the MLBP system as a function of the power factor. The value of lattice thermal conductivity is 37.15 W/mK at room temperature and follows the inverse dependency with temperature. With the anticipated superior performance, profound thermoelectric applications can be achieved particularly in the monolayer black phosphorous system.

cond-mat.mtrl-sci↗

arXiv2018

Non collinear Magnetism and Phonon Dispersion Relation in Vacancy Induced Phosphorene Monolayer

We have studied the electronic, magnetic and linear phonon dispersion behavior of Phosphorene monolayer using rst principle based ab initio method. Phosphorene monolayer is a semiconducting system with a dimensional dependent variable range of band gap. Vacancy has been done to study the geometry and physical behavior of the monolayer system. Pristine, vacancy induced monolayer and vacancy induced doped monolayer are included in the calculation. Dopant concentration has been well checked via optimization algorithm to maintain the dilute magnetic semiconducting behavior of the monolayer system. Density of states and partial density of state indicates the contribution of individual orbitals in the system. Band closing nature in observed in vacancy and doped vacancy states indicating closed dense states and metallic behavior of the perturbed phases. Both antiferromagnetic and ferromagnetic ordering is included in our calculation to get a charm of both ordering in the physical properties of the system. Landau energy level distribution is mapped via Fermi surface with linear dispersion relation in terms of phonon vibrational density of states and linear dispersion relations. The results of linear phonon density of states corroborating with electronic density of states.

cond-mat.mtrl-sci↗

arXiv2018

Surface modified mesoporous g-C3N4@FeNi3 as prompt and proficient magnetic adsorbent for crude oil recovery

Efficient oil adsorption and recovery is a generous universal importance for future energy demand and environmental protection. Adsorbents based on 2D flatland with engineered surfaces can overcome the limitations of conventional methods for selective oil adsorption. Here, we report magnetic hydrophobic/oleophilic graphitic C3N4 nanosheets that exhibit excellent oil sorption performance and rapid removal of adsorbed oil using an external magnet. Combining porous and nanosheets structure along with magnetic FeNi3 and fatty acid surface functionalization make the system an efficient adsorbent for adsorbing and separating crude oil from water. The graphitic sheets selectively adsorb crude oil with enhancement of thickness up to 9 folds and mass by 4.5 times than the pristine nanocomposite system. The smart adsorption property of g-C3N4@FeNi3 has been realized through comprehensive adsorption kinetics and inclusive isotherm studies. The nanocomposite can be further recycled and reused in an eco-friendly manner for oil adsorption and recovery.

physics.app-ph↗