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BEGIN:VEVENT
DTSTAMP:20261020T025115Z
LAST-MODIFIED:20181114T192926Z
DTSTART:20181107T193000Z
DTEND:20181107T203000Z
UID:event2045@bu.edu
URL:http://physics.bu.edu/internal/events/show/2045
SUMMARY:Interaction of Phonons and Dirac Fermions on the (001) Surface of t
	he Topological Crystalline Insulator Pb_{1-x}Sn_{x}Se
DESCRIPTION:Featuring Samuel Kalish\n\nPart of the Departmental Seminars.\n
	\nInteraction of Phonons and Dirac Fermions on the (001) Surface of the Top
	ological Crystalline Insulator Pb_{1-x}Sn_{x}Se\n\nDissertation Committee:\
	n\nMichael El-Batanouny\, Claudio Chamon\, Karl Ludwig\, John Butler\, Wanz
	heng Hu\n\nAbstract:\n\n\nNontrivial topological crystalline insulator phas
	es are protected by a crystal symmetry and not by time-reversal symmetry as
	 is the case of topological insulators. In this talk\, I will begin by disc
	ussing the theory of topological crystalline insulators. I will then argue 
	the merits of helium atom surface-scattering as a probe of surface dynamics
	\, and describe the techniques used. Next\, I will present inelastic scatte
	ring measurements to determine the surface phonon dispersion of the (001) s
	urface of the topological crystalline insulator Pb_{0.7}Sn_{0.3}Se. This ma
	terial exhibits a temperature-dependent topological transition\, so I have 
	made measurements of the surface phonon dispersion curves in both the trivi
	al and topological phases. I carry out calculations of the surface lattice 
	dynamics to interpret these measurements. I find that a vertical shear surf
	ace resonance branch around 1.9 THz dramatically changes on going from the 
	trivial to the topological phase. This remarkable change is associated with
	 the emergence of surface Dirac fermions. I use the measured dispersion of 
	this resonance branch to determine the corresponding momentum-dependent mod
	e-specific electron-phonon coupling λ_ν (q).
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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