arXiv subjects

Rohin Sharma

Publications and source records attributed to Rohin Sharma.

4 recordsLinked to original sources

arXiv2025

Magnetism at the interface of $MoSe_2/V_2O_5$ heterostructures

Magnetism in doped transition metal dichalcogenide monolayers and van der Waals interfaced materials have motivated the search for sustainable magnetic states at the nanoscale with the prospect of building devices for spintronics applications. In this study, we report the existence of magnetism in a heterostructure made up of an $MoSe_2$ transition metal dichalcogenide monolayer and a $V_2O_5$ substrate. Using density functional theory simulations, we find that ferromagnetic ordering can be found in the $MoSe_2/V_2O_5$ heterostructure even though the individual components are nonmagnetic. By examining the electronic structure and magnetic properties of this system we find how the occurring ferromagnetism evolves if the transition metal dichalcogenide or the $V_2O_5$ substrate can host point defects. Our study suggests that the balance between charge transfer and spin reorganization can lead to interface magnetism in novel hybrid materials.

cond-mat.mtrl-sci↗

arXiv2023

Upconversion of infrared light by graphitic micro-particles due to photo-induced structural modification

Recent reports of upconversion and white light emission from graphitic particles warrant an explanation of the physics behind the process. We offer a model, wherein the upconversion is facilitated by photo-induced electronic structure modification allowing for multi-photon processes. As per the prediction of the model, we experimentally show that graphite upconverts infrared light centered around 1.31~$μ$m to broadband white light centered around 0.85 $μ$m. Our results suggest that upconversion from shortwave infrared ($\sim$3~$μ$m) to visible region may be possible. Our experiments show that the population dynamics of the electronic states involved in this upconversion process occur in the timescale of milliseconds.

physics.optics↗

arXiv2023

Relativistic Tight-Binding Model for Hexagonal Lattice: Application to Graphene

A non-perturbative relativistic tight-binding (TB) approximation method applicable to crystalline material immersed in a magnetic field was developed in 2015. To apply this method to any material in the magnetic field, the electronic structure of the material in absence of a magnetic field must be calculated. In this study, we present the relativistic TB approximation method for graphene in a zero magnetic field. The Hamiltonian and overlap matrix is constructed considering the nearest neighbouring atomic interactions between the $s$ and $p$ valence orbitals, where the relativistic hopping and overlap integrals are calculated using the relativistic version of the Slater-Koster table. The method of constructing the Hamiltonian and overlap matrix and the resulting energy-band structure of graphene in the first Brillouin zone is presented in this paper. It is found that there is an appearance of a small band-gap at the $\textbf{K}$ points (also known as the spin-orbit gap) due to the relativistic effect, whose magnitude is $25$ $μ$eV.

cond-mat.mtrl-sci↗

arXiv2022

Determining size of an optically trapped particle via modulated Raman spectroscopy

The average Raman signal power obtained in a modulated optical trap is dependent on the Brownian motion - therefore hydrodynamic properties of the trapped particle. Hence, in addition to the molecular properties obtained from the Raman signal, it is possible to study hydrodynamic properties (e.g. size) of the particle by analyzing the change in the average Raman power as a function of modulation frequency. Our results, based on the over-damped Langevin equation, show that several minimas exist for the Raman signal at unique modulating frequencies for a given particle size and signal acquisition time. In typical experimental conditions, such minimas can be as low as 50% of the Raman signal in an unmodulated trap.

physics.optics↗