arXiv subjects

Vikrant Chaudhary

Publications and source records attributed to Vikrant Chaudhary.

7 recordsLinked to original sources

arXiv2026

Pressure-driven structural phase transition unlocks multifunctionality in KMgX (X = P, As, Sb, and Bi) compounds: A first-principles study

The search for materials with multifunctional properties has attracted significant attention due to their potential applications in various energy-related devices. Pressure-induced phase transitions provide an effective strategy for accessing different structural phases of a material without altering its chemical composition, thereby enabling the tuning of its physical properties and expanding its functional applications. In this work, we investigate the previously unexplored orthorhombic (Pnma) phase of the KMgX (X = P, As, Sb, and Bi) family using first-principles calculations and identify a pressure-induced structural transition from a tetragonal to orthorhombic phase. Stability of the pressure-accessible orthorhombic structure is rigorously confirmed by equation of state analysis together with phonon, elastic, and formation-enthalpy calculations, establishing its viability for further investigation. Optical properties calculated within the $G_0W_0$-Bethe-Salpeter equation (BSE) framework, incorporating quasiparticle corrections and excitonic effects, exhibit direct dipole-allowed transitions at the $\Gamma$ point and strong visible-light absorption with coefficients approaching $10^5~\text{cm}^{-1}$. Consequently, KMgAs and KMgSb achieve spectroscopic limited maximum efficiencies (SLME) of $27.12\%$ and $26.40\%$, respectively, at a thin-film thickness of $0.6~\mu\text{m}$. Furthermore, thermoelectric transport calculations predict (zT) values of 0.65 and 0.58 at $900~\text{K}$ for p-type and n-type KMgSb, respectively, demonstrating its potential for both legs of thermoelectric devices. These values are likely conservative, as the Slack model tends to overestimate thermal conductivity. Overall, the pressure-accessible orthorhombic phase of the KMgX family emerges as a stable multifunctional semiconductor with coupled photovoltaic and thermoelectric energy-conversion capabilities.

cond-mat.mtrl-sci↗

arXiv2026

Medium-Throughput Evaluation of Quantum Geometry-Driven Topological Transports in Altermagnets

Altermagnets provide a promising platform for a wide spectrum of applications integrating advantages of conventional ferromagnets and antiferromagnets. In this work, we implement a medium-throughput first-principles workflow and evaluate topological transport properties driven by quantum geometry for 135 altermagnets in the MAGNDATA database. Based on automated Wannier construction, both linear and nonlinear responses, including the anomalous Hall effect, magneto-optical Kerr effect, and bulk photovoltaic effect, are evaluated with further symmetry verifications. Detailed analysis is done on representative cases like metallic VNb3S6 with enhanced anomalous Hall conductivity, CaIrO3 with giant MOKE, and CuFeS2 with large shift current in non-centrosymmetric. These results establish a symmetry-guided computational route for identifying experimentally accessible fingerprints and functional transport properties in altermagnets.

cond-mat.mtrl-sci↗

arXiv2026

2D Ferroelectric Ruddlesden-Popper Perovskites: an Emerging Fully Electronically Controllable Shift Current and Persistent Spin Helix

Two-dimensional (2D) hybrid organic--inorganic perovskites (HOIPs) are promising candidates for next-generation optoelectronic and spintronic applications. This work systematically investigates the relationship between structural distortions and functional responses in three $C_{2v}$-symmetric Ruddlesden--Popper (RP) ferroelectric perovskites, $(4,4\text{-DFPD})_{2}\mathrm{PbI}_{4}$, $(\mathrm{DFCHA})_{2}\mathrm{PbI}_{4}$, and PEPI, using first-principles calculations combined with irreducible representation decomposition and wave-vector point-group symmetry (WPGS) analysis. The results reveal that the lead--iodide framework yields shift-current (SC) magnitudes comparable to, and in specific cases even an order of magnitude larger than, those of traditional ferroelectric oxides, with PEPI reaching a maximum of $69.16\ \mu\mathrm{A}/\mathrm{V}^{2}$. The SC magnitude correlates positively with the octahedral distortion index ($D_i$), while a competition mechanism is identified between covalent bond strength and structural asymmetry, where increased average bond lengths can offset the enhancement induced by $D_i$. Regarding spintronics, $C_{2v}$ symmetry-protected persistent spin textures (PST) are identified. A transition to $C_2$-protected quasi-PST occurs in monoclinic $(4,4\text{-DFHHA})_{2}\mathrm{PbI}_{4}$, leading to a persistent spin helix (PSH) with long-distance spin transport. The synergy among ferroelectricity, SC, and PST enables nonvolatile electrical control of both photocurrent direction and spin configurations. This work provides evaluation criteria and practical guidance for designing high-performance integrated spintronic--photovoltaic devices.

cond-mat.mtrl-sci↗

arXiv2025

High-throughput screening of spin Hall conductivity in 2D materials

Two-dimensional (2D) materials with large spin Hall effect (SHE) have attracted significant attention due to their potential applications in next-generation spintronic devices. In this work, we perform high-throughput (HTP) calculations to obtain the spin Hall conductivity (SHC) of 4486 non-magnetic compounds in the \texttt{2Dmatpedia} database and identify six materials with SHC exceeding $500\,(\hbar/e)\,(\mathrm{S/cm})$, surpassing those of previously known materials. Detailed analysis reveals that the significant SHC can be attributed to spin-orbit coupling (SOC)-induced gap openings at Dirac-like band crossings. Additionally, the presence of mirror symmetry further enhances the SHC. Beyond the high-SHC materials, 57 topological insulators with quantized SHCs have also been identified. Our work enables rapid screening and paves the way for experimental validation, potentially accelerating the discovery of novel 2D materials optimized for spintronics applications.

cond-mat.mtrl-sci↗

arXiv2024

Reflections from the 2024 Large Language Model (LLM) Hackathon for Applications in Materials Science and Chemistry

Here, we present the outcomes from the second Large Language Model (LLM) Hackathon for Applications in Materials Science and Chemistry, which engaged participants across global hybrid locations, resulting in 34 team submissions. The submissions spanned seven key application areas and demonstrated the diverse utility of LLMs for applications in (1) molecular and material property prediction; (2) molecular and material design; (3) automation and novel interfaces; (4) scientific communication and education; (5) research data management and automation; (6) hypothesis generation and evaluation; and (7) knowledge extraction and reasoning from scientific literature. Each team submission is presented in a summary table with links to the code and as brief papers in the appendix. Beyond team results, we discuss the hackathon event and its hybrid format, which included physical hubs in Toronto, Montreal, San Francisco, Berlin, Lausanne, and Tokyo, alongside a global online hub to enable local and virtual collaboration. Overall, the event highlighted significant improvements in LLM capabilities since the previous year's hackathon, suggesting continued expansion of LLMs for applications in materials science and chemistry research. These outcomes demonstrate the dual utility of LLMs as both multipurpose models for diverse machine learning tasks and platforms for rapid prototyping custom applications in scientific research.

cs.LG↗

arXiv2023

Effect of hydrostatic pressure and alloying on thermoelectric properties of van der Waals solid KMgSb: An \textit{ab-initio} study

Through a combined first-principles and Boltzmann transport theory, we systematically investigate the thermal and electrical transport properties of the unexplored ternary quasi two-dimensional KMgSb system of KMgX (X = P, As, Sb, and Bi) family. Herein, the transport properties of KMgSb under the application of hydrostatic pressure and alloy engineering are reported. At a carrier concentration of $\sim8\times10^{19}~\mathrm{cm^{-3}}$, the figure of merit zT ($\sim0.75$) for both the $n$-type and $p$-type of KMgSb closely matched, making it an attractive option for engineering both legs of a thermoelectric device using the same material. This is particularly desirable for high-performance thermoelectric applications. Furthermore, the zT value increases as pressure decreases, further enhancing its potential for use in thermoelectric devices. In the case of substitutional doping (replacing 50 \% Sb by Bi atom), we observed $\sim49~\%$ (in-plane) increase in the peak thermoelectric figure of merit (zT). The maximum zT value obtained after alloy engineering is $\sim1.45$ at 900~K temperature. Hydrostatic pressure is observed to be a great tool to tune the lattice thermal conductivity ($κ_L$). We observed that the negative pressure-like effects could be achieved by chemically doping bigger-size atoms, especially when $κ_L$ is a property under investigation. Through our computational investigation, we explain that hydrostatic pressure and alloy engineering may improve thermoelectric performance dramatically.

cond-mat.mtrl-sci↗

arXiv2023

Spin and current transport in the robust half-metallic magnet $c$-CoFeGe

Spintronics is an emerging form of electronics based on the electrons' spin degree of freedom for which materials with robust half-metallic ferromagnet (HMF) character are very attractive. Here we determine the structural stability, electronic, magnetic, and mechanical properties of the half-Heusler (hH) compound CoFeGe, in particular also in its cubic form. The first-principles calculations suggest that the electronic structure is robust with 100 \% spin polarization at the Fermi level under hydrostatic pressure and uni-axial strain. Both the longitudinal and Hall current polarization are calculated and the longitudinal current polarization ($P_{L}$) is found to be $>99\%$ and extremely robust under uniform pressure and uni-axial strain. The anomalous Hall conductivity (AHC) and Spin Hall conductivity (SHC) of hH cubic CoFeGe (\textit{c}-CoFeGe) are found to be $\sim -100$ S/cm and $\sim 39~\hbar/e$ S/cm, respectively. Moreover, the Curie temperature of the alloy is calculated to be $\sim$524 K with a 3 $μ_{B}$ magnetic moment. Lastly, the calculated mechanical properties indicate that \textit{c}-CoFeGe is ductile and mechanically stable with a bulk modulus of $\approx$ 154 GPa. Overall, this analysis reveals that cubic CoFeGe is a robust half-metallic ferromagnet and an interesting material for spintronic applications.

cond-mat.mtrl-sci↗