title: Anomalous weak magnetism in superconducting YBa2Cu3O6+x.
abstract: For some time now, there has been considerable experimental and theoretical effort to understand the role of the normal-state "pseudogap" phase in underdoped high-temperature cuprate superconductors. Recent debate has centered on the question of whether the pseudogap is independent of superconductivity. We provide evidence from zero-field muon spin relaxation measurements in YBa2Cu3O6+x for the presence of small spontaneous static magnetic fields of electronic origin intimately related to the pseudogap transition. Our most significant finding is that, for optimal doping, these weak static magnetic fields appear well below the superconducting transition temperature. The two compositions measured suggest the existence of a quantum critical point somewhat above optimal doping.
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. jeff_sonier@sfu.ca
authors.forename: J E
authors.initials: JE
authors.lastname: Sonier
authors.forename: J H
authors.initials: JH
authors.lastname: Brewer
authors.forename: R F
authors.initials: RF
authors.lastname: Kiefl
authors.forename: R I
authors.initials: RI
authors.lastname: Miller
authors.forename: G D
authors.initials: GD
authors.lastname: Morris
authors.forename: C E
authors.initials: CE
authors.lastname: Stronach
authors.forename: J S
authors.initials: JS
authors.lastname: Gardner
authors.forename: S R
authors.initials: SR
authors.lastname: Dunsiger
authors.forename: D A
authors.initials: DA
authors.lastname: Bonn
authors.forename: W N
authors.initials: WN
authors.lastname: Hardy
authors.forename: R
authors.initials: R
authors.lastname: Liang
authors.forename: R H
authors.initials: RH
authors.lastname: Heffner