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Magnetoresistance from Quantum Interference Effects in Topological Materials

Speaker:Dr. Bo Fu
Affiliation:Department of Physics, The University of Hong Kong
Date:September 23, 2019 (Monday)
Time:2:30 p.m.
Venue:Room 518, 5/F, Chong Yuet Ming Physics Building, HKU


A large amount of experimental results about the longitudinal magnetoresistance (LMR) in Weyl semimetal and topological insulator systems display a nonmonotonic behavior over a wide range of magnetic field conditions. At small fields close to zero, a sharp increase of the LMR is observed. When the magnetic field exceeds some threshold value, the LMR is found to decrease as the magnetic field increases. In experiment, this crossover from positive to negative magnetoresistivity is commonly attributed to the competition between Chiral anomaly and weak antilocalization. This negative magnetoresistivity is viewed as the signature of chiral anomaly and the evidence for the existence of Weyl fermion. Using the Feynman diagram techniques, we derive the magnetoconductivity formulae from the quantum interference effects for disordered three-dimensional Dirac materials. By including all the possible contributing Cooperon modes, we can reproduce such nonmonotonic magnetoresistance behavior. We also find that by changing the chemical potential, topological trivial and non-trivial insulators exhibit distinctly different magnetoconductivity behavior. It can help us to directly distinguish the different topological phases through the bulk states transport measurement.

Coffee and tea will be served 20 minutes prior to the seminar.

Anyone interested is welcome to attend.