Research

Low temperature dissipation phenomena in Nano-electrical-Mechanical-system

We have studied the mechanical response of nano-mechanical resonators from temperatures ranging from 10 mK to 2 K. At lowest temperatures dissipation in solids are generally dominated by defects that can be modeled by tunneling two level systems (TLS). There is a lack of good data required for understanding TLS mechanisms in the nano scale in various materials. We have measures the dissipation in metallic beams and now we will be trying to measure the dissipation in superconducting beams.

Recently we were able to tune the dissipation in Pd NEMS by adding Hydrogen, which could be due to the enhance phonon-TLS coupling. We also observed saturation in low temperature dissipation, which may possibly be due to Dicke super-radiance between TLS and phonon. you can have a look at this paper:10.1103/PhysRevB.95.214113

A typical NEMS device
A typical NEMS device
Dissipation and frequency respons e of the Pd beam

Spin current and spin fluctuation measurements in diffusive metallic systems 

We are trying to measure the spin current in diffusive metallic system based on non local geometry in nano scale device. PI has already measured the pure spin current in 2DEG’s during is post-doc. More ambitions aim is to measure the spin fluctuations in these devices using 1/f noise method.

A spin injection device with non-local geometry prepared in our lab.
A spin injection device with non-local geometry prepared in our lab.
Spin Current measured in 2DEG
Spin Current measured in 2DEG

Sensing of Hydrogen with 1/f noise

We are trying to make sensor for Hydrogen using 1/f noise technique. 1/f noise is a unique technique which can probe a fluctuating entity, it can be either external defects or  vacant site, so in this way this technique is more powerful than just measuring the resistance of the device. We have fabricated devices using e-beam lithography.

Optical microscope image of the device to measure noise.
Optical microscope image of the device to measure noise.
Preliminary data on the device.
Preliminary data on the device.