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METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20260815T080556Z
LAST-MODIFIED:20161021T185027Z
DTSTART:20161028T160000Z
DTEND:20161028T170000Z
UID:event1645@bu.edu
URL:http://physics.bu.edu/internal/events/show/1645
SUMMARY:Optical manipulation of electronic bands using Floquet-Bloch States
DESCRIPTION:Featuring Nuh Gedik\, MIT\n\nPart of the Biophysics/Condensed M
	atter Seminar Series.\n\nThe coherent optical manipulation of solids is eme
	rging as a promising way to engineer novel quantum states of matter. The st
	rong time-periodic potential of intense laser light was predicted to genera
	te hybrid photon–electron states named Floquet–Bloch states. In this ta
	lk\, I will report on first experimental observation of these states in top
	ological insulators (TI). Using time- and angle-resolved photoemission spec
	troscopy\, we show that an intense ultrashort mid-infrared pulse with energ
	y below the bulk band gap of TI hybridizes with the surface Dirac fermions 
	of a topological insulator to form Floquet-Bloch bands. The photon-dressed 
	surface band structure is composed of a manifold of Dirac cones evenly spac
	ed by the photon energy and exhibits polarization-dependent band gaps at th
	e avoided crossings of the Dirac cones. Circularly polarized photons induce
	 an additional gap at the Dirac point\, which is a signature of broken time
	-reversal symmetry on the surface. Beyond topological insulators\, manipula
	tion of electronic bands via light matter interaction holds great promise i
	n many other systems as well. I will illustrate this with our recent measur
	ements on monolayer semiconducting transition-metal dichalcogenides in whic
	h we were able to break valley degeneracy using off-resonant circularly pol
	arized light.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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