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New quantum transport phenomena under large electric and magnetic fields

March 27, 2018 - 4:00pm
Speaker: 
Liang Fu
Institution: 
MIT

The discovery of topological insulators and semimetals has brought into focus Berry phase effects on transport properties of quantum solids. This talk will begin with an overview of anomalous Hall effect driven by Berry phase mechanism. I will then turn to two new transport phenomena. The first is the second-order Hall effect, by which a transverse current occurs in second-order response to an external electric field. I will show that the nonlinear Hall conductivitiy in the DC or low-frequency limit can be nonzero in time-reversal-invariant and inversion-breaking materials, and is governed by the dipole moment of Berry curvature in momentum space.

The second part of this talk is on thermoelectric effect under a large magnetic field. I will show that the thermopower of semimetals and narrow-gap semiconductors can be dramatically boosted in the quantum limit. In particular, the thermopower of Dirac/Weyl semimetals increases with the field without saturation and can reach extremely high values. These theoretical results suggest an immediate pathway for achieving record-high thermopower and thermoelectric figure of merit, and compare well with a recent experiment on Pb1−xSnxSe.

Hosted by: Brian Swingle

Physical Sciences Complex Lobby