arXiv subjects

Tanusri Saha Dasgupta

Publications and source records attributed to Tanusri Saha Dasgupta.

5 recordsLinked to original sources

arXiv2026

MXene with Janus Structure at Transition metal site -A route to Emergent Properties

Motivated by the discovery of bimetallic MXene compounds with Janus metal sites, we investigate Janus MXenes TiM"CO2, where M" = Mo, W. Our computational analysis reveals that broken inversion symmetry in the Janus structure, coupled with strong spin-orbit coupling at M", generates diverse and remarkable functionalities. These include pronounced Rashba spin splitting, non-trivial Z2 topology, Berry-curvature-dipole-driven nonlinear anomalous Hall effect, and strain control of the Berry curvature dipole. Notably, the 4d transition-metal-based TiMoCO2 and 5d transition-metal-based TiWCO2, with M" elements from the same column of the periodic table, display markedly different behaviors. While TiMoCO2 is a Z2 topological insulator, TiWCO2 is a trivial semimetal. Both compounds, however, exhibit compelling quantum properties. TiWCO2 shows a robust Rashba effect with a large Rashba coefficient of 1.35 eV. Angstrom and a large nonlinear anomalous Hall conductivity of 120 x 0.0001 G0. TiMoCO2, a Z2 narrow-gap semiconductor with weaker Rashba splitting and moderate nonlinear anomalous Hall conductivity, exhibits a strain-driven transition from semiconductor to semimetal. This transition modulates both the sign and magnitude of the Berry curvature dipole, yielding a sizable nonlinear anomalous Hall conductivity of 17 X 0.0001 G0 under 2% tensile strain. Our findings underscore the potential of MXenes as a platform for investigating and tailoring multifunctional quantum phenomena.

cond-mat.mtrl-sci↗

arXiv2025

Role of topotactic hydrogen in Superconductivity of Infinite-layer Nickelate NdNiO$_{2}$: A first-principles and variational Monte Carlo study

Employing combination of first-principles calculations, low-energy model construction, and variational Monte Carlo solution of the ab-initio derived Hubbard model, we study the effect of hydrogenation in the electronic structure and superconducting properties of infinite-layer nickelate, NdNiO$_2$. We find that the introduction of hydrogen at the apical oxygen vacancy position strongly influences the Wannier function corresponding to the effective interstitial orbital at the Ni site bound to the hydrogen. This results in the near disappearance of the electron pocket at the $k_z$ = $π$ Fermi surface, keeping that of $k_z$ = 0 unchanged, compared to the dehydrogenated case. The two-band model thus remains valid even in the presence of H. The calculated superconducting order parameters both in absence and presence of H, show a two-hump superconductivity arising the two overlapping domes, one arising from $d_{x^{2}-y^{2}}$ and another arising from interstitial orbital degree of freedom. Hydrogenation strengthens the latter, marginally affecting the former.

cond-mat.supr-con↗

arXiv2025

Unusual Valence of Ru and Prediction of Magnetism, Anomalous Hall Conductivity in a Newly Synthesized Double Perovskite Compound Ca_2CoRuO_6

With a goal to expand on the family of double perovskite compounds, hosting 3d transition metal and 4d or 5d transition metal, two new ordered double perovskite compounds, Ca$_2$FeRuO$_6$ and Ca$_2$CoRuO$_6$ are synthesized following the prediction of a recent high throughput machine-learning study [Phys. Rev. Materials 3, 084418]. Experimentally both compounds are found to stabilize in monoclinic symmetry, which is consistent with the high-throughput prediction for Ca$_2$FeRuO$_6$, but at odd for Ca$_2$CoRuO$_6$. Among the two synthesized compounds, the properties of Ca$_2$CoRuO$_6$, investigated employing the first principles technique and model Hamiltonian calculation, appear promising. The monoclinic structured Ca$_2$CoRuO$_6$ is found to stabilize unusual 6+ valence of Ru, and support a half-metallic ground state with uncompensated net moment. As predicted by our first-principles study, the finite spin-orbit coupling at the Ru site contributes to the non-trivial topology of the band structure of monoclinic Ca$_2$CoRuO$_6$, resulting in a moderately large value of anomalous Hall conductivity. Our theoretical predictions should encourage further experimental investigation of this newly synthesized compound.

cond-mat.mtrl-sci↗

arXiv2024

Inter-chain Interactions, Multi-magnon condensation and Strain effect in chain compound NaVOPO$_4$

Employing first-principles modelling and many-body methods, the magnetic properties of spin-1/2 chain compound NaVOPO$_4$ are explored. The extensive first-principles calculations establish an intricate three-dimensionally coupled model that consists of weakly alternating $J$-$J^{\prime}$ antiferromagnetic chains running along cris-cross directions between two consecutive $ab$ planes, connected via two subleading couplings, a ferromagnetic exchange along the $c$ direction ($J_c$) and a weaker antiferromagnetic exchange ($J_a$) along the body diagonal direction. The exact diagonalization and density matrix renormalized group study has been carried out on a two-dimensional spin model with $J$-$J^{\prime}$-$J_c$ and effective $J_d$ couplings, constructed based on the full model, for numerical ease. The $J_c$-$J_d$ phase diagram is found to host a {\it disorder} phase with a finite spin gap for comparable values of $J_c$ and $J_d$, arising out of the competing nature of these two interactions, other than two ordered phases. The calculated thermodynamic properties of this model provide a fair description of experimentally measured data. The predominant manifestation of $J_c$ and $J_d$ in the disorder phase happens in the stabilisation of a multi-magnon condensed phase, upon gap closing by application of an external magnetic field. We further explore the effect of tensile uniaxial strain, which is found to drive the system from gapful to gapless ground state.

cond-mat.str-el↗

arXiv2023

Ab-initio Insights on the Fermiology of $d^1$ Transition metals in Honeycomb lattice : Hierarchy of hopping pathways and spin-orbit coupling

Motivated by the intriguing suggestion of realizing SU(8) Dirac semi-metal with $J=3/2$ electrons on a honeycomb lattice, we provide a systematic study of the interplay of various hopping pathways and atomic spin-orbit coupling for the low energy electrons in candidate d$^1$ transition metal halides MX$_3$ (M=Ti, Zr, Hf; X=F, Cl, Br). By combining first principle calculations and minimal hopping Hamiltonian, we uncover the role of dominant direct metal-metal hopping on top of indirect metal-halide-metal hopping. This sets up a hierarchy of hopping pathways that centrally modify the SU(8) picture for the above materials. These hopping interactions, along with the spin-orbit coupling, lead to a plethora of exactly compensated metals instead of the SU(8) Dirac semi-metal. Remarkably the same can be understood as descendants of a topological insulator obtained by gapping out the SU(8) Dirac semi-metallic phase. The resultant compensated metals have varied Fermi surface topology and are separated by Lifshitz phase transitions. We discuss the implications of the proximate Lifshitz transition, which may be accessed via strain, in the context of the relevant materials.

cond-mat.str-el↗