Vorticity and phase coherence in high Tc.ppt

1. Introduction 2. Vortex Nernst effect 3. Enhanced ism 4. Fragile London rigidity T> Tc 5. Low-temp. Quantum Vortex Liquid State Vorticity and the Phase Diagram of Cuprates Lu Li, J. G. Checkelsky , . Princeton Univ. Yayu Wang, Princeton U., . Berkeley M. J. Naughton , Boston College S. Ono, S. Komiya, Yoichi Ando, CRI, Elec. Power Inst., Tokyo S. Uchida, Univ. Tokyo Genda Gu , Brookhaven National Lab Hong Kong Univ , Dec. 2006 1. (1975-80) Sliding charge density waves (LRA) Pinning and Depinning , FLR length 2. (1980-84) Gang of four, weak localization, oresistance , dephasing 3. (1987-2000) RVB and Gauge theories of cuprate pairing (NL, WL) 4. (1995-98) Thermal conductivity of Dirac quasiparticles Thermal Hall effect and qp -vortex scattering 5. (2000 -- ) Strong fluctuations in pseudogap state BC AD Thanks, Patrick! hole s = 1/2 Phase diagram of cuprates T pseudogap T *T c Mott insulator Fermi liquid doping x (fraction of sites with holes) vortex liquid dSC AF Spontaneous vorticity destroys superfluidity Josephson Effect, phase-slip and Nernst signal t ?V J2? Phase difference Passage of a vortex Phase diff. ? jumps by 2 ? Integrate V J to give dc signal prop. to n v ???? J eV 2 = 2 ?hn V Josephson Eq . Nernst effect experiment Vortices move in a temperature gradient Phase slip generates Josephson voltage 2 eV J = 2 ?h n VE J = B x v e y = E y /| T | (Nernst signal) Tc Nernst signal persists high above T c Bi 2212 (UD) Wang et al. PRB 2001 Giant Nernst signal in cuprates overdoped optimal underdoped Wang, Li, NPO PRB 2006 Nernst signal e N = E y /| T | Vortex-Nernst signal in Bi 2201 Wang, Li, Ong PRB 2006 ? Condensate amplitude persists to T onset > T c ? Nernst signal confined to SC dome ? Vorticity defines Nernst region Nernst region Kosterlitz Thouless transition in 2D superconductor Unbinding of vortex- antivortex ? F = U - TS Free energy gain vortex density vortex antiv