Magnetic Tunnel Junctions: These are nano devices, whose structure is a sandwich of a thin insulator barrier in between two ferromagnets. The insulator supports current via tunneling mechanism when the spins on both sides of the junction are the same. Otherwise the device exhibits high resists. This way the device acts as a two state switch. Such a device was first proposed by Dutta and Das in 1980s and is now realized experimentally after the discovery of Giant magnetoresistance and consequently Tunnel magnetoresistance. We work on fabricating and characterizing MTJs with novel 2D layers as tunnel barriers.
Novel 2D materials: It all began with a scotch tape nobel prize winning discovery! Once Geim and Novoselov discovered graphene, this avalanched progress in semiconductor technological industry. Graphene also gave a deeper picture of the quantum world. But the constraint is the zero bandgap nature of graphene. Many other 2D materials like h-BN, MoS2 have been of importance to research since they exhibit promising features that edge over graphene. Heterostructures of these 2D materials make very useful devices for tunnel junctions, magnetic memory devices, spin valves etc. We characterize these novel materials to probe into the quantum phase transitions that they display at low temperatures. We also work fabricating magnetic tunnel junctions with these 2D layers.
Spin Hall systems: When an unpolarized current is passed through the length of the sample, spatial separation of electrons is observed in the transverse direction to the current depending on the electron spin. This occurs dominantly in materials with significant spin-orbit coupling strength. Instead of current through an applied bias, we choose to provide a temperature gradient along the longitudinal direction and this leads to spin separation in transverse direction to the temperature gradient. This is known as the Spin Seebeck effect. We fabricate devices of the order of nano scale and measure the spin Seebeck signal in the devices. Our interests are in measuring the spin Seebeck signal in materials like Au, transition metal dichalcogenides etc.
Thermoelectrics: We have in-house built Seebeck measurement set-up. We investigate Seebeck co-effficient as a function of temperature for metals, semiconductors and bulk 2D materials.