arXiv subjects

Bidyut Mallick

Publications and source records attributed to Bidyut Mallick.

4 recordsLinked to original sources

arXiv2025

Neel order, spin-spiral, and spin liquid ground state in frustrated three dimensional system CaMn2P2: A DFT+U and spin dynamics study

We investigate the magnetic ground state and phase transitions in the frustrated three-dimensional system CaMn2P2 using first-principles calculations combined with spin-dynamics simulations. Our DFT+U calculations reveal that CaMn2P2 exhibits an indirect gap semiconducting ground state with a localized Mn2+ electronic configuration and negligible spin-orbit coupling effects. The computed exchange interactions show that the magnetic behavior is well described by a isotropic Heisenberg Hamiltonian. In this model, there are two major couplings: the NN interaction J1 couples the two Mn layers along the c-axis and next NN J2 is in the a-b plane where Mn ions form a hexagonal layer structure. Our results show that both J1 and J2 are antiferromagnetic in nature and as a consequence J2 induce frustration owing to the in-plane triangular geometry of the Mn-ions. The J1 is found to promote long-range antiferromagnetic order, while the J2 is responsible for spin canting and disorder. Our spin-wave analysis confirms that the system stabilizes a spin-spiral ground state with a propagation vector q = (1/6 , 1/6, 0) in agreement with neutron diffraction experiments. By tuning the J2/J1 ratio, we construct a phase diagram that reveals a transition from a collinear Neel antiferromagnetic state to different spin-spiral phases, and eventually to a disordered phase at large frustration. Atomistic spin-dynamics simulations capture the temperature evolution of the magnetism and reproduce the experimentally measured magnetic data with good accuracy. Furthermore, for large J2/J1, we identify a low temperature phase with slow spin relaxation and persistent fluctuations, suggesting a spin-liquid like state. Our study provides an understanding of frustration induced magnetism in CaMn2P2 and establishes it as a realization of J1-J2 model in three-dimensional lattice for exploring emergent magnetic phases.

cond-mat.str-el↗

arXiv2025

Charge-state dependent spin-orbit coupling and quantum phase transitions in Ir-Ru oxides

The competition between kinematic, relativistic and Coulombic interactions in iridium-based oxides has spurred intense experimental and theoretical investigations regarding the electronic structure and magnetism. We argue here that the Iridium-Ruthenium triple perovskites, Ba$_3$MRuIrO$_9$ (M = Li, Mg and In), are of particular interest in this regard. We show here, using ab-initio theory, that the nominal charge states of Ir can be tuned from +6 to +4 by choosing non-magnetic 'M' ions as Li (+1), Mg(+2) and In (+3). This variation modulates the influence of the spin-orbit coupling (SOC) which is found here to be negligible in Ba$_3$LiRuIrO$_9$, moderate in Ba$_3$MgRuIrO$_9$ and determining in Ba$_3$InRuIrO$_9$. Our analysis classifies Ba$_3$LiRuIrO$_9$ as a band-insulator, Ba$_3$MgRuIrO$_9$ as a SOC and correlation driven insulator and Ba$_3$InRuIrO$_9$ as $J_{\rm eff} = 1/2$ Mott-Hubbard insulator. As reported here, correlated electronic structure theory results in sizeable magnetic moments of both Ru and Ir atoms in these systems and atomistic spin-dynamics simulations capture the experimental N\'eel temperature for Ba$_3$LiRuIrO$_9$ and Ba$_3$MgRuIrO$_9$ and provide evidence for a phase transition for Ba$_3$InRuIrO$_9$ when T $\to$ 0 K, to a multi-valley magnetic state with strong magnetic frustration. The theory identifies the presence of Kitaev interaction among the iridium atoms in Ba$_3$InRuIrO$_9$. The realization of such strong anisotropic interactions helps to stabilize a particularly complex energy landscape of Ba$_3$InRuIrO$_9$, that opens up for exotic magnetic quantum phases.

cond-mat.str-el↗

arXiv2024

Pressure induced insulator-to-metal transition in few-layer FePS$_3$ at 1.5 GPa

In two-dimensional (2D) van der Waals (vdW) layered materials the application of pressure often induces a giant lattice collapse, which can subsequently drive an associated Mott transition. Here, we investigate room-temperature layer-dependent insulator-metal transition (IMT) and probable spin-crossover (SCO) in vdW magnet, FePS$_3$, under high-pressure using micro-Raman scattering. Experimentally obtained spectra, in agreement with the computed Raman modes, indicate evidence of IMT of FePS$_3$ started with a thickness-dependent critical pressure ($P_c$) which reduces to 1.5 GPa in trilayer flakes compared to 10.8 GPa for the bulk counterpart. Using a phenomenological model, we argue that strong structural anisotropy in few-layer flakes enhances the in-plane strain under applied pressure and is, therefore, ultimately responsible for reducing the critical pressure for the IMT with decreasing layer numbers. Reduction of the critical pressure for phase transition in vdW magnets to 1-2 GPa marks the possibility of using intercalated few-layers in the field-effect transistor device architecture, and thereby, avoiding the conventional use of the diamond anvil cell (DAC).

cond-mat.mes-hall↗

arXiv2018

Molecular dynamics simulations reveal the role of ceramicine B as novel PPARγ partial agonist against type 2 diabetes

Peroxisome proliferator-activated receptors gamma (PPARγ) are ligand-activated controllers of various metabolic actions and insulin sensitivity. PPARγ is thus considered as an important target to treat type 2 diabetes. Available PPARγ drugs (full agonists) have robust insulin-sensitizing properties but are accompanied by severe side effects leading to complicated health problems. Here, we have used molecular docking and a molecular dynamics simulation study to find a novel PPARγ ligand from a natural product. Our study suggests that the inhibition of ceramicine B in the PPARγ ligand-binding domain (LBD) could act as a partial agonist and block cdk5-mediated phosphorylation. This result may provide an opportunity for the development of new anti-diabetic drugs by targeting PPARγ while avoiding the side effects associated with full agonists.

q-bio.BM↗