arXiv subjects

Prafulla K Jha

Publications and source records attributed to Prafulla K Jha.

5 recordsLinked to original sources

arXiv2026

Interplay of Altermagnetism and Coupled Quasi-Altermagnetic states in Sliding Two-dimensional Square Lattice

The emergence of non-relativistic spin splitting (NRSS) in altermagnetic systems has introduced a new paradigm in antiferromagnets with vanishing net magnetization. Although sliding-induced valley-polarized phases have recently been demonstrated in two-dimensional altermagnets, the observed valley-polarized state represents only a partial manifestation of altermagnetism, and a comprehensive classification based on spinsplitting characteristics remains lacking. Here, using first-principles calculations, general stacking theory, and spin-Laue symmetry analysis, we propose a coupled quasialtermagnetic state representing a distinct subclass of altermagnetism, in which reversible type-IV NRSS is controlled through interlayer sliding. Accordingly, the sliding-induced phases are classified into two categories: altermagnetic and quasi-altermagnetic states. We establish a direct correspondence between reciprocal-space spin splitting and real-space switching between the two quasi-altermagnetic states. Importantly, the spin-polarized bands in these states remain spin split at {\Gamma} point even in the absence of spin-orbit coupling (SOC), distinguishing them within the proposed classification framework. To demonstrate the interplay between altermagnetic and quasi-altermagnetic states, we investigate the two-dimensional Lieb-lattice material Mn2WS4 and its Janus derivative Mn2WS2Se2, analysing how changes in the local environment influence the different magnetic phases. Importantly, the underlying mechanism is broadly applicable to a wide class of twodimensional square-lattice systems. We further investigate the effects of SOC, focusing on spin texture and transport signatures in coupled quasi-altermagnetic states.

cond-mat.mtrl-sci↗

arXiv2023

Non-trivial topological phases in transition metal rich half-Heusler Oxides

Topological Insulators with gapless surface states and insulating bulk in non-centrosymmetric cubic systems have been extensively explored following the discovery of two-dimensional quantum spin hall effect in zincblende HgTe. In such systems the negative band inversion strength E$_{BIS}$ ($=$ E$_{Γ_6} -$ E$_{Γ_8} <$ 0) governs the robustness of the non-trivial topological states at ambient conditions. Hence, realizing large negative values of E$_{BIS}$ has been a guiding motivation of several investigations reported in literature. Here, we present a material design approach which can be employed to realize large negative values of E$_{BIS}$ in cubic materials such as half-Heusler (HH) oxides with 18 valence electron configurations. We explore 27 HH oxides of the form ABO (A = Li, K, Rb; B = Cu, Ag, Au) in $α$-, $β$-, and $γ$-phase (by placing transition metal atom at different Wyckoff positions) for their non-trivial topological phase. Off these three phases, we found that, the $α$-phase of nine HH oxides (wherein the transition metal atoms occupy 4a Wyckoff positions in the crystal structure) is the most promising with non-trivial topological phase which is governed by the mass-darwin relativistic effects enhancing E$_{BIS}$. Whereas the other phases were found to be either trivial semiconductors or semimetals or metals and most of them being dynamically unstable. We focus on RbAuO in $α$-phase with E$_{BIS}$ of $-$ 1.29 eV and the effect of strain fields on the topological surface states of this compound. We conclude that the $α$-phase of HH oxide presented here can be synthesized experimentally for diverse room temperature applications in spintronics and nanoelectronics.

cond-mat.mtrl-sci↗

arXiv2019

A first-principles investigation of Topological Phase Transition in face-centred cubic LiMgBi

Topological Insulators (TI) exhibit robust spin-locked dissipationless Fermion transport along the surface states. In the current study, we use \textit{first-principles} calculations to investigate a Topological Phase Transition (TPT) in a Half-Heusler (HH) compound LiMgBi driven by a Volume Expansive Pressure (VEP) which is attributed to the presence of, intrinsic voids, thermal perturbations and/or due to a phenomena known as cavity nuclei. We find that, the dynamically stable \textit{face-centred cubic} (FCC) structure of LiMgBi (which belongs to the F$\overline{4}$3m[216] space group), undergoes TPT beyond a critical VEP at 4.0\%. The continuous application of VEP from 0.0\% to 8.0\% results in a phase transition from a, band insulator to a Dirac semi-metal nature. Qualitatively, the Dirac cone formation and band inversion along the high symmetry point $\mathbfΓ$ in the Brillouin Zone (BZ) are analysed in terms of Electronic Band Structure (EBS) and Projected Local Density of States (LDOS). The TPT is further characterised by the $\mathbb{Z}_2$ invariant, ($ν_0$, $ν_1$ $ν_2$ $ν_3$) $\equiv$ (1, 0 0 0) along the (0001) surface which indicates quantitatively that, HH LiMgBi is a strong TI. We hence propose, HH LiMgBi (known for its piezoelectric, thermo-electric and semi-conducting applications) as a strong TI with potential multipurpose application in the field of electronics, spintronics and quantum computation.

cond-mat.mtrl-sci↗

arXiv2018

On detection and annihilation of spherical virus embedded in a fluid matrix at low and moderate Reynolds number

Effect of high and low Reynolds number is studied on low frequency vibrational modes of a spherical virus embedded in the aqueous medium. We have used an analytical approach based on fluid dynamic and classical Lamb theory to calculate the vibrational modes of a virus with material parameters of lysozyme crystal in water. The obvious size effect on the vibrational modes is observed. The estimated damping time which is of the order of picosecond varies with Reynolds number and shows a high value for a critical Reynolds number. The stationary eigenfrequency regions are observed for every quantum number l and n suggesting the most probable Re ranges for acoustic treatment of viruses in order to detect or annihilate the virus using corresponding viruswater configuration.

cond-mat.soft↗

arXiv2017

Tailoring the Electronic and Magnetic Properties of Peculiar triplet-ground-state Polybenzoid Triangulene

In the present work we have studied the structural and electronic properties of recently synthesized elusive free standing triangulene using density functional theory. Triangulene, which is a type of graphene quantum dot, is a molecule with an even number of electrons and atoms but the structure of molecule is such that it is impossible to pair all these electrons.

cond-mat.mes-hall↗