Experimental demonstration of Fermi surface effects at filling factor 5/2.
Using small wavelength surface acoustic waves (SAW) on ultrahigh mobility heterostructures, Fermi surface properties are detected at 5/2 filling factor at temperatures higher than those at which the quantum Hall state forms. An enhanced conductivity is observed at 5/2 by employing sub-0.5-microm SAW, indicating a quasiparticle mean-free path substantially smaller than that in the lowest Landau level. These findings are consistent with the presence of a filled Fermi sea of composite fermions, which may pair at lower temperatures to form the 5/2 ground state.
Willett
R L
RL
Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA.
West
K W
KW
Pfeiffer
L N
LN