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Colloquia
Colloquium
Friday, April 26, 2013
4:00 PM
Physics Building, Room 204
Note special time.

Philip Kim
[Host: Seunghun Lee]
Columbia University
"Bloch, Landau, and Dirac: Hofstadter's Butterfly in Graphene"
Slideshow (PDF)

ABSTRACT:
Electrons moving in a periodic electric potential form Bloch energy bands where the mass of electrons are effectively changed. In a strong magnetic field, the cyclotron orbits of free electrons are quantized and Landau levels forms with a massive degeneracy within. In 1976, Hofstadter showed that for 2dimensional electronic system, the intriguing interplay between these two quantization effects can lead into a selfsimilar fractal set of energy spectrum known as "Hofstadter's Butterfly." Experimental efforts to demonstrate this fascinating electron energy spectrum have continued ever since. Recent advent of graphene, where its Bloch electrons can be described by Dirac fermions, provides a new opportunity to investigate this half century old problem experimentally. In this presentation, I will discuss the experimental realization Hofstadter's Butterfly via substrate engineered graphene under extremely high magnetic fields controlling two competing length scales governing DiracBloch states and Landau orbits, respectively. 
SLIDESHOW:




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