Superconductor–Insulator Transitions in Ultra-thin <i>a</i>-Pb Films: Disorder, Magnetic-field, and Magnetic-impurity Tuning

Peng Xiong, Ashwani Kumar, H. Jeffrey Gardner and Liuqi Yu

in Conductor-Insulator Quantum Phase Transitions

Published in print June 2012 | ISBN: 9780199592593
Published online September 2012 | e-ISBN: 9780191741050 | DOI:
Superconductor–Insulator Transitions in Ultra-thin a-Pb Films: Disorder, Magnetic-field, and Magnetic-impurity Tuning

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The superconductor-insulator quantum phase transitions tuned by three independent parameters: disorder, paramagnetic impurity and perpendicular magnetic field, have been directly compared in the same homogeneous ultrathin a-Pb films. The magnetic impurity-tuned transition is characterized by progressive suppression of the critical temperature to zero and a continuous transition to a weakly insulating normal state with increasing impurity density. In all key aspects, the disorder-tuned transition closely resembles the magnetic impurity-tuned transition. The magnetic field-tuned transition appears qualitatively different, and in many aspects resembles the behavior of the superconductor-insulator transition in granular films which is a canonical example of a bosonic transition. In the critical region, the field-tuned transition exhibits transport behavior that suggests magnetic field induced mesoscale phase separation and presence of Cooper pairing in the insulating state.

Keywords: superconductor-insulator transition; disorder; paramagnetic impurity; magnetic field; phase separation; Cooper pair insulator

Chapter.  7627 words.  Illustrated.

Subjects: Mathematical and Statistical Physics

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