Topological signatures in electronic transport

• Applicant: Dr. Eslam Khalaf, Ph.D.
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2018 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 402840991

The study of topological phenomena and their influence on physical behavior has been one of the most intensively investigated scientific topics of the past few decades. Topological band structures, topological excitations and topological defects play a very important role in understanding puzzling experimental finding in a diverse class of physical systems. In addition, they offer a new venue to harness the quantum mechanical nature of electrons in a wide range of applications including quantum computers and spintronic devices. The most prominent experimental signature of topology is provided by electronic transport experiments, which is the main focus of the proposed projects. The first project investigates transport in materials possessing linear band touching points known as Weyl nodes. These are topological defects in a band structure that can only be annihilated by being brought together. Upon application of magnetic field, the existence of Weyl nodes leads to a significant drop in electrical conductance along the direction of the applied field and our goal is to investigate the influence of disorder on such an effect. The second project investigates the potential connection between the unusual transport observed in a class materials with helimagnetic spin order, e.g. MnSi, and the recently observation of topological defects in the spin structure of these materials. The third project investigates transport properties of a two-dimensional electron gas subject to strong magnetic field when the lowest Landau level is half-filled. It has been known for some time that the behavior of electrons in this system is described in terms of composite objects formed by combining an electron with two flux quanta. A recent proposal suggested that these composite objects are Dirac particles and our main objective in this project is to investigate possible transport signatures of such particles.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Ashvin Vishwanath