title: Magneto-optical evidence for a gapped fermi surface in underdoped YBa2Cu3O6+x.
abstract: The infrared (900-1100 cm(-1)) Faraday rotation and circular dichroism are measured in the normal state of underdoped High T(c) superconductors and used to study the magnetotransport. YBa2Cu3O6+x thin films are investigated in the temperature range 10-300 K in magnetic fields up to 8 T and as a function of oxygen concentration. A dramatic increase of the Hall frequency is observed for underdoped samples, which is not consistent with the approach to a Mott transition but is consistent with a partial gapping of the Fermi surface as predicted in density wave models.
authors.affiliation: Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Rigal
authors.forename: D C
authors.initials: DC
authors.lastname: Schmadel
authors.forename: H D
authors.initials: HD
authors.lastname: Drew
authors.forename: B
authors.initials: B
authors.lastname: Maiorov
authors.forename: E
authors.initials: E
authors.lastname: Osquiguil
authors.forename: J S
authors.initials: JS
authors.lastname: Preston
authors.forename: R
authors.initials: R
authors.lastname: Hughes
authors.forename: G D
authors.initials: GD
authors.lastname: Gu