title: Superconductivity. Quasiparticle mass enhancement approaching optimal doping in a high-T(c) superconductor.
abstract: In the quest for superconductors with higher transition temperatures (T(c)), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. Recent experiments have suggested the existence of the requisite broken-symmetry phase in the high-T(c) cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. We used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa2Cu3O(6+δ) over a wide range of doping, and observed magnetic quantum oscillations that reveal a strong enhancement of the quasiparticle effective mass toward optimal doping. This mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p(crit) ≈ 0.18.
authors: Mail Stop E536, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. bradramshaw@gmail.com.
authors: B J
authors: BJ
authors: Ramshaw
authors: Cavendish Laboratory, Cambridge University, Cambridge CB3 OHE, UK.
authors: S E
authors: SE
authors: Sebastian
authors: Mail Stop E536, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors: R D
authors: RD
authors: McDonald
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z4, Canada.
authors: James
authors: J
authors: Day
authors: Cavendish Laboratory, Cambridge University, Cambridge CB3 OHE, UK.
authors: B S
authors: BS
authors: Tan
authors: Mail Stop E536, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors: Z
authors: Z
authors: Zhu
authors: Mail Stop E536, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors: J B
authors: JB
authors: Betts
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z4, Canada. Canadian Institute for Advanced Research, Toronto M5G 1Z8, Canada.
authors: Ruixing
authors: R
authors: Liang
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z4, Canada. Canadian Institute for Advanced Research, Toronto M5G 1Z8, Canada.
authors: D A
authors: DA
authors: Bonn
authors: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z4, Canada. Canadian Institute for Advanced Research, Toronto M5G 1Z8, Canada.
authors: W N
authors: WN
authors: Hardy
authors: Mail Stop E536, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors: N
authors: N
authors: Harrison