arXiv subjects

Sonam Phuntsho

Publications and source records attributed to Sonam Phuntsho.

4 recordsLinked to original sources

arXiv2025

Modulation of Spin-Orbit Coupling, Spin Textures, and Rashba-Edelstein Response in Chiral Tellurium: A First-Principles Study

Chiral semiconductors such as elemental tellurium (Te) exhibit unconventional spin textures and large charge-to-spin conversion efficiencies, yet the influence of introducing elements on these properties remains underexplored. Here, we address this gap by investigating how substituting Te with lighter (S, Se) or heavier (Sb) elements systematically modifies the spin-orbit-driven phenomena in chiral Te, including the band structure, spin Berry curvature, and Rashba-Edelstein response. The objective is to determine whether elemental substitution strategies can be leveraged to optimize collinear spin textures, enhance spin accumulation, and possibly extend spin lifetimes all crucial aspects for magnet-free spintronics. Using density functional theory calculations implemented in Quantum ESPRESSO, combined with tight-binding interpolation in PAOFLOW, we map out the element-dependent electronic states and quantify their associated spin transport coefficients. Our findings reveal that lighter elements shift the Fermi level to regions of pronounced spin splitting, thereby increasing the magnitude of spin-current conversion, whereas heavier elements can introduce or remove near-degenerate bands that strongly affect spin-orbit coupling. In both scenarios, the fundamental chirality of Te remains robust, preserving the radial or ''collinear'' spin-momentum locking. These results not only confirm that introducing elements is a potent and feasible route for tuning spin-orbit phenomena but also offer practical guidelines for experimental efforts aiming to engineer chiral semiconductors for spin devices. By correlating element identity with specific spin-texture enhancements, this study paves the way for rationally designing next-generation spintronic components free from external magnetic fields.

cond-mat.mtrl-sci↗

arXiv2025

Enhanced Thermoelectric Performance through Site-Specific Doping in Tetragonal Cu$_{2}$S: A First-Principles Study

This work investigates how site-specific doping can enhance the thermoelectric performance of tetragonal Cu$_{2}$S using Density functional Theory and Projected Atomic Orbital Framework for Electronic Transport. We address the gap in current research, where most doping studies focus on the high-temperature cubic polymorph, leaving the tetragonal structure underexplored. By substituting Cu with Li, Na, or Mg, as well as partially replacing S with Se or Te, we systematically examine changes in electronic structure and transport properties. Our results reveal that cation-site doping can strongly shift the Fermi level. In particular, Li doping enhances the power factor ($σS^2$) by optimizing carrier concentrations and band-edge alignments, whereas Mg, due to its divalent nature, offers a higher carrier density but requires careful balancing to maintain a large Seebeck coefficient. On the anion side, substituting heavier chalcogens (Se or Te) reshapes the valence bands and subtly shifts the Fermi level, yielding moderate improvements in both electrical conductivity and Seebeck coefficient. These doping-induced alterations, captured through transport calculations, demonstrate a clear route for tailoring the interplay between conductivity and thermal transport toward potentially high figure-of-merit values. Overall, the findings highlight the importance of site specificity in doping strategies for tetragonal Cu$_{2}$S, showing that judicious choice of dopant elements and concentrations can significantly improve key thermoelectric metrics. Such insights provide a foundation for experimental validation and further development of Cu$_{2}$S-based materials for mid- to high-temperature thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2024

Influence of Functional Group on the Self Assembly of Diamondoids: A Molecular Dynamics Study

This study investigates the molecular-level self-assembly behavior of seven functionalized diamondoids, examining how diverse substituents influence structural organization, thermal stability, and aggregate morphology. Using a combination of density functional theory for initial geometry optimization and molecular dynamics simulations, we explored radial distribution functions, thermal fragmentation temperatures, and radii of gyration for each system. Our results reveal that hydrogen-bonding and polar functional groups (e.g., amino, hydroxy) foster well-defined, ordered assemblies, while bulkier or less interactive substituents (e.g., phenyl, methoxy) lead to more open, amorphous aggregates. Thermal stability strongly depends on substituent chemistry: complex, bulky groups or heteroatom-rich functionalities confer enhanced resistance to fragmentation at high temperatures, whereas simpler groups destabilize the assembly at lower temperatures. Radii of gyration further show that substituent size and polarity can fine-tune cluster compactness. These findings provide critical insights for designing diamondoid-based nanomaterials with tailored structural properties, thermal endurance, and functional performance in advanced technological applications.

cond-mat.mes-hall↗

arXiv2024

Impact of Lipid Structural Variations on Bilayer Properties: A Coarse-Grained Molecular Dynamics Study

The supramolecular assembly of lipids into bilayer membranes is essential for cellular structure and function. However, the impact of lipid structural variations such as acyl chain length, degree of unsaturation, and headgroup type on bilayer properties remains incompletely understood. This study employs coarse-grained molecular dynamics simulations using the Martini force field to investigate seven distinct lipid species, aiming to compute critical bilayer parameters including area per lipid, bilayer thickness, and lateral diffusion coefficients. Our simulations reveal that lipids with longer acyl chains exhibit increased bilayer thickness, while unsaturation introduces kinks in the acyl chains, generally reducing bilayer thickness and increasing the area per lipid. Lipids with unsaturated chains demonstrate higher lateral diffusion coefficients, enhancing membrane fluidity. Variations in headgroup chemistry significantly influence lipid packing and membrane dynamics. This investigation advances our understanding of membrane biophysics and has significant implications for the design of lipid-based systems in biomedical applications.

cond-mat.soft↗