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PRODID:UW-Madison-Physics-Events
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SEQUENCE:1
UID:UW-Physics-Event-4555
DTSTART:20171019T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T021518Z
LAST-MODIFIED:20171011T180451Z
LOCATION:5310 Chamberlin
SUMMARY:Cyclotron resonance in graphene: Kohn’s theorem\, many-parti
 cle physics\, and more\, R. G. Herb Condensed Matter Seminar\, Erik He
 nriksen \, Washington University in St. Louis
DESCRIPTION:Cyclotron resonance—the resonant absorption of infrared 
 light by charge carriers in a strong magnetic field– is one of the m
 ore basic measurements that can be made on semiconductors. First demon
 strated on germanium in the early ‘50s\, CR proved to be enormously 
 useful in determining semiconductor band structures and\, from the ‘
 70s\, was instrumental in probing two-dimensional systems in Si and Ga
 As heterostructures. However\, early on W. Kohn pointed out a limitati
 on of the CR technique: in translationally invariant parabolic systems
 \, CR is insensitive to electron-electron interactions\, with the cons
 equence that CR has been useless in investigating such remarkable phen
 omena as the fractional quantum Hall effect. We have performed CR meas
 urements over the past decade that demonstrate how to evade Kohn’s t
 heorem by breaking translational invariance\, or working in graphene w
 hose linear dispersion can be viewed as an extreme case of a non-parab
 olic band structure. In our most recent work we find direct evidence o
 f many-particle physics in the cyclotron resonance of high mobility gr
 aphene. This exciting development suggests that infrared spectroscopy 
 will provide a new window on interacting electron phenomena in graphen
 e including (fractional) quantum Hall effects\, Hofstadter’s butterf
 ly\, hydrodynamic transport\, and perhaps even cavity QED. <br>
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URL:https://www.physics.wisc.edu/events/?id=4555
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