I am interested in the physics and simulations of electronic transport in nano-electronic and spintronic devices devices and in optical properties of materials in the quantum limit. Expertise in the simulation of devices of length comparable to the atomic scale is the main theme of our work. Such simulations are mainly based on Non-equilibrium Green’s function (NEGF) formalism, and the many body density matrix/Fock space approach depending on the regime of application in electron, spin, and energy transport. A brief description of the methods we use in simulations are given below:

Non equilibrium Green's function formalism

When length of the devices becomes shorter than the mean free path, classical approach like drift-diffusion equation fails to give us adequate insights and correct results in simulations. The electron distribution inside the channel in such cases can't be described by a quasi fermi distribution. Moreover parameters in classical approach like mobility, diffusion length, mean free path can't be defined in such devices. NEGF is a method of computational simulation of such devices using quantum mechanical approach. This approach enables us to simulate devices whose length is shorter or comparable to the mean free path. Things like electron-phonon scattering, spin-magnon scattering and spin orbit coupling can easily be accounted for by choice of suitable parameters. With technology scaling in nanometre range, NEGF becomes important in theoritical device simulation.

Fock Space Approach

Fock Space approach offers suitable method of simulation of single electron transistors/ molecular quantum dots. In the sequential tunneling/coulomb blockade limit, NEGF method becomes unsuitable for device simulation. NEGF method relies on an average self consistent potential to account for electron-electron interaction. This average self consistent potential becomes meaningless or undefined in sequential tunneling/coulomb blockade limit due to potential variation inside the quantum dot with varying electronic occupation number (due to high charging energy/self capacitance of such dots/transistors). In such cases the Fock space approach can provide an accurate description of electronic transport through the system.

Density Functional Theory

Density functional theory is mainly used to find the band-structure information of devices. Software like quantumwise (licensed) and quantum espresso (free) provide a suitable platform for DFT simulations.