QUANTUM-RELATIVISTIC TRANSPORT PHENOMENA IN DIRAC METALS
Abstract
PROJECT SUMMARY The goal of this proposal is understand the transport properties of three-dimensional (3D) Dirac materials. This new class of materials are characterized by the Dirac equation, which combines the physics of the Schr¨odinger equation with special relativity [1]. In this sense they are similar to graphene, but with the crucial difference that 3D Dirac andWeyl semi-metals manifest these effects in (3+1) dimensions (where +1 refers to time). These systems have recently emerged as a central focus of the condensed matter community due to the prediction of exotic effects connected to their relativistic character. For both applied and fundamental reasons, the most important of these are their transport properties. The focus of this proposal will be on the study of topological surface states that are protected from (large-angle) scattering [2–8], the (local) non-conservation of charge (the so-called chiral anomaly [6, 8–12]), and a strain-dependent anomalous Hall effect [3, 13]. Revealing these effects in real materials is non-trivial. Firstly, they are strongly anisotropic effects, and depend delicately on the projection of electric and magnetic fields with respect to the crystallographic axes. This requires geometrically well defined current paths, which are difficult to achieve because the crystals are very small (down to ?10?m on a side [14] in some cases) and because they usually grow in a preferred direction, which may not be the physically interesting one. Secondly, some of the properties I am interested involve exotic surface effects, but these are often swamped by bulk properties. In my view, we need to rethink how to perform transport experiments in these kinds of materials, requiring innovations in sample preparation and measurement. I utilize my synthesis and experimental capabilities to allow transport behavior to be measured with unprecedented accuracy in any geometric configuration as a function of applied electric and magnetic field and on samples ranging from microns to millimeters in size - 3 orders of magnitude in scale. This work will not only reveal the exotic transport effects in 3D Dirac systems for the first time, but will open a new experimental pathway for the characterization of relativistic quantum materials. I have divided up this overall vision into three targeted objectives: (i) Transport and quantum oscillations from Fermi arcs. The topological nature of DSM and WSM leads to novel surfaces states that connect chiral Weyl states [2, 7]; (ii) Electric and magnetic field scaling in the chiral anomaly. The topological nature of the Weyl nodes leads to the nonconservation of charge, dramatically increasing the magneto-conductivity in a way that should scale in both magnetic and electric fields [2, 9]. (iii) Symmetry breaking topological phase transitions. Time-reversal and lattice symmetries can be used to drive topological and superconducting phase transitions [3]. These scientific targets alone are ground breaking, but the impact of this proposal is much deeper. The materials synthesized in my lab are shared through my domestic and international collaborations. The knowledge gained through these allows me to put together a broad physical picture of these systems, greatly facilitating scientific progress. Moreover, this significantly extends the reach of this proposal, since my materials will be crucial to the research of a network of scientific groups.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512674
Entities
People
- James Analytis
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents