BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20260827T160602Z
LAST-MODIFIED:20170203T145412Z
DTSTART:20170209T203000Z
DTEND:20170209T213000Z
UID:event1720@bu.edu
URL:http://physics.bu.edu/internal/events/show/1720
SUMMARY:Shining light on topological insulators and Weyl semimetals
DESCRIPTION:Featuring Liang Wu\, University of California\, Berkeley\n\nPar
	t of the Biophysics/Condensed Matter Seminar Series.\n\nThe last decade has
	 witnessed an explosion of research investigating the role of topology in b
	and-structure\, as exemplified by the wealth of recent works on topological
	 insulators (TIs) and Weyl semimetals (WSMs). In this talk I hope to convin
	ce you that optical probes of solids give unique insight into these topolog
	ical states of matter. First\, I will discuss how we can probe the special 
	low-energy electrodynamics of 3D TI thin films of Bi2Se3 using time-domain 
	THz spectroscopy[1].  I will then discuss our work following the evolution 
	of the response as a function of magnetic field from a semi-classical trans
	port regime [2] to a quantum regime [3].   In the later case\, although DC 
	transport is still semi-classical\, we find evidence for Faraday and Kerr r
	otation angles quantized in units of the fine structure constant [3].   Thi
	s is consistent with the long-sought "axion electrodynamics" and the topolo
	gical magneto-electric effect of 3D TIs.  Among other aspects this give a p
	urely solid-state measure of the fine structure constant based on a topolog
	ical invariant [3]. I will also discuss how optics can observe quantized Ha
	ll conductance without involving the edge states [3]. Finally\, I will pres
	ent our most recent discovery of the largest 2nd harmonic generation in tra
	nsition monopnictide Weyl semimetals such as TaAs [4] and talk about a new 
	perspective of nonlinear optics in term of probing the Berry connection/cur
	vature in momentum space [4]. (The focus of my talk will be on Refs. [3\, 4
	].)\n\n1. Wu\, et al\, Nat. Phys. 9\, 410-414 (2013).\n2. Wu\, et al\, Phy.
	 Rev. Lett. 115\, 217602  (2015).\n3. Wu\, et al\, Science 354\, 1124-1127 
	(2016). \n4. Wu\, et al\, Nat. Phys. (2016). doi:10.1038/nphys3969
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR