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DTSTAMP:20190421T181138Z
LAST-MODIFIED:20181114T192926Z
DTSTART:20181107T193000Z
DTEND:20181107T203000Z
UID:event2045@bu.edu
URL:http://physics.bu.edu/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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