The role of dual-nuclear baths on singlet-triplet dynamics in a double quantum dot
Bhaskaran Muralidharan, Indian Institute of Technology Bombay
A deeper understanding of electronic transport phenomena at the nanoscale is a cross-disciplinary effort that intertwines quantum dynamics, electronic structure and statistical physics. Beginning with the basic tenets of nanoscale transport that forms the basis of modern nanoelectronic device theory, we allude to various applications of this theory to a wider array of applications spanning energy efficient switching [1], nano and spintronic energy harvesting [2-5] and fundamental limits of computing, following which we specifically focus on spin qubit manipulation in quantum dots [5]. Spin-blockaded electronic transport across a double quantum dot (DQD) system represents an important advancement in the area of spin-based quantum information. The basic mechanism underlying the blockade is the formation of a blocking triplet state [5]. The bistability of the leakage current as a function of the applied magnetic field in this regime is believed to arise from the effect of nuclear Overhauser fields [5] on spin-flip transitions between the blocking triplet qubit and the conducting singlet states. The objective of this talk is to present the nuances of considering a two bath model on the experimentally observed current bistability by employing feedback models of the nuclear spin dynamics coupled with the electronic transport of the DQD set up [5]. In doing so, we first discuss the important subtleties involved in the microscopic derivation of the hyperfine mediated spin flip rates. We then give insights as to how the differences between the two nuclear baths and the resulting difference Overhauser field affect the two-electron qubit states of the DQD, and their connection with the experimentally observed current hysteresis curve. We finally allude to how the set up may be used to understand the stochastic dynamics involved in “demon” like feedbacks and how such interactions may lead to quantum information flow.
References:
[1] N. Chatterji, A. A. Tulapurkar and B. Muralidharan, Appl. Phys. Lett., 105, 232410,(2014).
[2] B. Muralidharan and M. Grifoni, Phys. Rev. B, 85, 155423, (2012).
[3] B. Muralidharan and M. Grifoni, Phys. Rev. B, 88, 045402, (2013).
[4] A. Agarwal and B. Muralidharan, Appl. Phys. Lett., 105,013104, (2014).
[5] S. Buddhiraju and B. Muralidharan, J. Phys.: Condens. Matter, 26, 485302, (2014).
BIO OF THE SPEAKER: 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 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 December 2015, he is an Associate Professor at the Department of Electrical Engineering at IIT Bombay, India. He is currently involved in the physics and simulation of non-equilibrium phenomena in a variety of systems including nanodevices, nano and spin thermoelectrics and fundamental limits of modern computation. He was also the recipient of the APS-IUSSTF professorship award in 2014.