Near-field Microwave Probing of Nontrivial Topological Boundary States
Abstract
The objective of this proposal is to locally probe the nanoscale conductivity distribution of quantum spin Hall and quantum anomalous Hall systems, with special focus on their topological edge channels, by near-field microwave impedance microscopy (MIM). The boundaries of these exotic quantum states can support dissipationless electrical transport and may serve as perfectly conducting channels in radio-frequency nanoelectronic and spintronic devices. While both effects have been successfully demonstrated by macroscopic measurements, much remains to be explored on the microscopic details of the edge states. Local probing of these exotic quantum states by the low-temperature MIM is there not only of great academic interest but also of technological importance to realize high-speed and low-power electronics for defense applications. Specifically, we will perform quantitative measurements on the widths of quantum spin Hall edges in InAs/GaSb quantum wells and quantum anomalous Hall edges in magnetically doped (Bi,Sb)2Te3 topological insulators. The effects of temperature, and magnetic field, and local perturbation due to a DC tip bias on the edge and bulk states will also be studied. The multi-domain formation and a network of chiral edges during the magnetization reversal in the quantum anomalous Hall systems will be investigated. The proposed research is significant because it aims at the fundamental understanding of nanoscale electronic structures of topologically ordered quantum states. The spatially resolved conductivity maps will provide critical feedback for material scientists to improve the sample quality and increase the onset temperatures of quantum spin Hall and quantum anomalous Hall states towards practical device applications. Moreover, the electrical properties of the edge and bulk states will be studied at the frequency spectrum of 0.1 Ð 10 GHz, which is the regime of interest for many defense applications.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 15, 2018
- Source ID
- W911NF1710542
Entities
People
- Keji Lai
Organizations
- Army Contracting Command
- United States Army
- University of Texas at Austin