Seminar featuring Bhaskaran Muralidharan, Indian Institute of Technology Bombay
Semiconductor nanowire-superconductor hybrid systems provide a promising platform for hosting unpaired Majorana fermions and thus realizing fault-tolerant topological qubits. In this talk, starting from the basic tenets of quantum transport theory, we demonstrate how to adapt the Non-Equilibrium Green’s Function (NEGF) formalism to model quantum transport in normal (N)-superconductor (S) junctions. We analyze Josephson junctions based on semiconductor nanowires and derive the Andreev bound state spectrum and current-phase relations.
Recently, [1], and [2] have reported oscillations in the critical supercurrent with an axial magnetic field. Our simulations indicate that this phenomenon arises from the interference of orbital angular momentum modes [3,4] of the cylindrical nanowire. We also add disorder and study its effect on the critical current oscillations, with an aim to gain a thoroughgoing understanding of the experiments. Finally, we also comment on the Majorana modes in a finite topological superconductor [5], and most importantly the transport signatures that detect them.
[1] K. Gharavi et.al., ArXiv:1405.7455v2, (2014).
[2] Zuo, et. al. Phys. Rev. Lett. 119, 187704 (2017)
[3] P. Sriram et. al., Phys. Rev B, 100, 155431, (2019).
[4] A. Lahiri et.al., Phys Rev B, 98, 125417, (2018).
[5] N. Leumer et.al., ArXiv:1909.10971, (2019).
Dr. Bhaskaran Muralidharan obtained his B.Tech in Engineering Physics from the Indian Institute of technology (IIT) Bombay in 2001, his M. S. and Ph. D in Electrical Engineering from Purdue University, West Lafayette, USA in 2003 and 2008 respectively. Between 2008-2012, he was a post-doctoral associate at the Massachusetts Institute of Technology (MIT) and at the Institute for theoretical Physics at the University of Regensburg, Germany. Since 2012, he has been a faculty in the Department of Electrical Engineering at IIT Bombay, where he is currently an associate professor. He was also the recipient of the APS-IUSSTF professorship award in 2014.