Biography
Prof. Somnath Bhattacharyya
Prof. Somnath Bhattacharyya
University of the Witwatersrand, India
Title: Spin triplet superconductivity in boron doped diamond through symmetry breaking effects and Spin valve behavior of Gd-functionalized carbon nanotubes
Abstract: 
The talk will focus on two aspects of magnetism in nanostructured carbon. Superconducting nanocrystalline boron doped diamond (films) have demonstrated a large spacial variation in the structure of the order parameter across individual samples, indicative of a mixed superconducting phase. Here we demonstrate the coexistence of spin-orbit coupling and superconductivity, and hence shed light on the nature of this mixed phase for the first time. Hallmark features of spin-orbit coupling are observed through the presentation of the weak anti-localization effect in the low field magneto-conductance. Ultra-high-resolution transmission microscopy indicates the microstructure is dominated by crystal twinning with grain boundaries composed of stacking fault planes where translational symmetry is sharply broken, this along with antisymmetric confinement potential between grains allows for a Rashba-type spin orbit coupling. Most importantly, a pronounced zero bias conductance peak in the differential conductance is observed, through the magnetic field dependence of this peak we establish a clear signature of a hidden triplet character. Spin mixing of singlet and triplet states is believed to occur due to a Rashba spin orbit coupling related to broken structural inversion symmetry at the diamond interfaces.
Biography: 
Somnath Bhattacharyya is a Professor in the School of Physics at the University of the Witwatersrand, Johannesburg, South Africa whose research is focused on the area of condensed matter physics and nano-electronics. In 1997 Somnath Bhattacharyya completed his doctoral degree from the Indian Institute of Science, Bangalore in Condensed Matter Physics. He worked as a researcher in the USA, Germany and England. His major interest is in the transport properties of carbon and major achievements include the demonstration of resonant tunnel devices based on amorphous carbon, gigahertz transport in carbon devices, n-type doping of nanocrystalline diamond and developing theoretical models for transport in disordered carbon and recently in unconventional superconductivity in diamond. In 2007 he established his new research group the “Nano-scale Transport Physics Laboratory” at the University of the Witwatersrand, Johannesburg in South Africa. His team focuses on the fabrication of the nanoelectronic devices, studying novel electronic properties of nanocrystalline diamond films and carbon superlattice structures at high magnetic fields and high frequencies. His group is also involved in performing theoretical modelling of carbon quantum structures as well as new quantum processors. Prof. Bhattacharyya has published four book chapters and about seventy papers in peer reviewed journals. At present Prof. Bhattacharyya is engaged in developing a new infrastructure for a wider range of quantum nanotechnology that will include qubits, quantum matter, carbon based microwave detectors, and also encourage deeper studies of philosophy of science.