Speaker
David Broun
(Simon Fraser University)
Description
David Broun, Simon Fraser University
Xiaoqing Zhou, Simon Fraser University
Benjamin Morgan, University of Cambridge
Wendell Huttema, Simon Fraser University
Darren Peets, University of British Columbia & Max-Planck-Institut für Festkörperforschung, Stuttgart
Patrick Turner, Simon Fraser University
John Waldram, University of Cambridge
Ahmad Hosseini, University of British Columbia
Ruixing Liang, University of British Columbia
Doug Bonn, University of British Columbia
Walter Hardy, University of British Columbia
High magnetic fields have played a key role in extending our understanding of the normal state of the cuprate superconductors to low temperatures. Early pulsed-field measurements, by Ando and Boebinger, revealed a transition in the underdoped regime to a state in which resistivity increases with decreasing temperature, with a puzzling log(1/T) form. Recent quantum oscillation studies have provided a wealth of additional information on electronic structure. However, the true nature of the nonsuperconducting ground state remains uncertain. A central issue is the role of local superconducting pairing in the pseudogap regime: to resolve this, a distinct physical signature of the presence of vortices is ideally needed.
Our measurements of flux-flow resistivity reveal that the transition from metallic low temperature resistivity to log(1/T) behaviour in fact occurs on the overdoped side of the phase diagram. Working deep within the superconducting phase, with the cleanest available samples of YBCO and Tl2201, we take a different approach from previous experiments and measure the response of vortices to microwave-frequency driving currents. This circumvents flux pinning and reveals a log(1/T) flux-flow resistivity that persists throughout the superconducting region of the cuprate phase diagram. This includes a regime at high carrier dopings in which the normal-state transport is Fermi-liquid-like, indicating that the log(1/T) flux-flow resistivity observed in the superconducting state is not simply a reflection of the normal state, but a dynamical property of the vortices themselves. This would imply, in turn, that the log(1/T) resistivity seen in the pseudogap phase is a signature of vortex fluctuations and therefore that local superconducting pairing persists to high magnetic fields in the underdoped cuprates.
Primary author
David Broun
(Simon Fraser University)
