Lloyd Engel

"Microwave and rf spectroscopy of two-dimensional electron solids"

When:

February 11, 2011

Time:

03:00 PM - 04:00 PM

Location:

PHYS 242

Speaker:

Lloyd Engel
National High Magnetic Field Laboratory, Florida State University

Details:

http://www.magnet.fsu.edu/search/personnel/getprofile.aspx?fname=Lloyd&lname=Engel&id=757032c5-7aa3-434f-9f88-07530fcef37d

Two-dimensional electron systems (2DES) in high magnetic field are well known for  the integer and fractional quantum Hall effects,   but   also have ground states  with broken spatial symmetry, including crystalline solids, and  phases with stripes of charge density.     The archetypical electron solid, expected to be the ground state of disorder-free 2DES in the high magnetic field  or low density limit, is the Wigner crystal, a triangular lattice of electrons stabilized by their mutual repulsion.   

We have found that a striking rf or microwave resonance in the spectrum is a generic feature of the electron solids or stripes, with observed resonance frequencies ranging from 70 MHz   to 10 GHz.   The electron solids are insulators due to pinning by disorder, and the resonances are interpreted as “pinning modes”,  in which crystalline domains oscillate within the disorder potential.    After introducing the phenomenology of the resonances, I will present results on  Wigner solids of exotic excitations of quantum Hall effects: skyrmions within the integer quantum Hall effect  at Landau filling n=1, and  fractionally charged quasiparticles  within the 1/3 fractional quantum Hall effect.