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Raman studies on chirality purified carbon nanotubes: quantum interference, Kohn anomalies and an introduction to metal dichalcogenides

Event Details

Event Dates: 

Thursday, September 19, 2013 - 12:00pm

Seminar Location: 

  • Duane Physics Room D142

Speaker Name(s): 

Hagen Telg

Speaker Affiliation(s): 

LANL
Seminar Type/Subject

Scientific Seminar Type: 

  • Condensed Matter Seminar

Event Details & Abstract: 

Beside their promising properties for future applications carbon nanotubes represent an excellent material system to study basic nanoscale physics. The first part of this seminar will be about a selection of effects and processes where nanotubes show a textbook behavior in terms of nanoscale physics.I will discuss how confinement affects the electronic bandstructure of carbon nanotubes resulting in a characteristic pattern of optical transitions. This pattern of narrow optical transition in SWCNT allows the observation of quantum inference which manifests in unusual lineshapes of resonant Raman profiles. Using the example of three particular nanotube chiralities I will demonstrate the effect of quantum interference and the role of the sign of the Raman matrix element on the observed Raman responds.Kohn anomalies in low dimensional materials are expected to be strongly enhanced. In metallic nanotubes this manifests in a strongly downshifted LO phonon. Recent results show that an additional Kohn anomaly is responsible for an observed upshift of the TO phonon frequency. In the second part of the seminar I will give an introduction to new physics in layered metal dichalcogenides including valley dependent optical selection rules and effects from strong manybody interactions.