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BEGIN:VEVENT
DTSTAMP:20261018T150843Z
LAST-MODIFIED:20180723T180344Z
DTSTART:20180725T163000Z
DTEND:20180725T173000Z
UID:event2003@bu.edu
URL:http://physics.bu.edu/internal/events/show/2003
SUMMARY:Large and quantized non-linear responses in chiral topological meta
	ls.
DESCRIPTION:Featuring Adolfo Grushin\, Institut Neel\, CNRS and Universite 
	Grenoble Alpes\, F-38042 Grenoble\, France\nHosted by: Claudio Chamon\n\nPa
	rt of the Condensed Matter Theory Seminar Series.\n\nIn this talk I will di
	scuss our recent results concerning nonlinear and linear responses of topol
	ogical chiral metals. We have recently predicted a quantized circular photo
	galvanic effect\, the part of the photocurrent which changes sign when the 
	light's polarization flips. We find it is quantized in units of a large uni
	versal constant\ne^3/h^2 times the Weyl monopole charge in mirror free Weyl
	 semimetals (e.g. SrSi2). Although not topologically protected\, this resul
	t extends beyond two band models to all chiral metals with multifold fermio
	ns\, which opens up the search to new materials. We identify a range of pre
	viously-unidentified ternary compounds able to exhibit chiral multifold fer
	mions of all types (including a range of materials in the families AsBaPt a
	nd Gd$_3$Cl$_3$C)\, and provide specific predictions for the known multifol
	d material RhSi.  As a side result we also calculate the gyrotropy of all c
	hiral multifold fermions\, which we find also to be enhanced compared to th
	e Weyl semimetal case.\n\nFinally\, if time permits I will discuss briefly 
	the measurement and modeling of the second harmonic generation in TaAs\, th
	e frequency doubling of an incident pulse upon reflection or transmission.\
	nExperimentally it is found to be extremely large and anisotropic compared 
	to materials in the same symmetry class such as GaAs. We show that these fe
	atures are well captured phenomenologically in terms of a model of coupled 
	ferroelectric chains\, which suggests that TaAs is close to saturating a ph
	otocurrent bound that we derive.\n\nRefs:\n\nF. de Juan\, AGG\, T. Morimoto
	\, J. E. Moore Nat. Comm. 8\, 15995 (2017)\n\nF. Flicker\, F. de Juan\, T. 
	Morimoto\, B. Bradlyn\, M. Vergniory\, AGG\narXiv:1806.09642\n\nS. Pakantar
	 et al. arXiv: 1804.06973
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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