Dirac Physics in Junctions of Topological Insulators
Krishenendu Sengupta, Indian Association for the Cultivation of Sciences
Over the past few years, there has been tremendous theoretical and experimental effort in condensed matter physics towards understanding the properties of a special class of insulating materials commonly referred to as called topological insulators. At present there are several known examples of such materials such as Bismuth Telluride. One of the key features of these insulators, in contrast to their conventional counterparts, is that their surfaces host massless electron like particles whose properties are well-described by Dirac-like equation, and hence, are in sharp contrast to those of standard electrons in ordinary metals. In this talk, I am going to discuss a few of these unconventional properties. First, I shall show that the spin of these electrons are locked along their direction of motion; a property commonly termed as helicity. Second, I shall discuss how the electrons on the surface of these topological insulators can move through a thin barrier without getting reflected for special values of the barrier strength; a phenomenon known in the literature as transmission resonance. Third, I shall show that these electrons have unconventional response to a magnetic field applied parallel to the surface on which they reside. Finally, I demonstrate that above-mentioned properties of these electrons may be used to design junctions of topological insulators whose conductance can be tuned by an applied magnetic field leading to their possible application as a magnetic switch.
Background Review Articles:
1) The quantum spin Hall effect and topological insulators. Xiao-Liang Qi and Shou-Cheng Zhang. Phys. Today 63, January, 33 (2010).
2) Tuning the Conductance of Dirac Fermions on the Surface of a Topological Insulator. S. Mondal, D. Sen, K. Sengupta, and R. Shankar. Phys. Rev. Lett. 104 046403 (2010).