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Sequential superconductor–Bose insulator–Fermi insulator phase transitions in quasi-two-dimensional α-WSi


Zhang, Xiaofu; Schilling, Andreas (2018). Sequential superconductor–Bose insulator–Fermi insulator phase transitions in quasi-two-dimensional α-WSi. Physical review. B, 97(21):214524.

Abstract

A zero-temperature magnetic-field-driven superconductor to insulator transition (SIT) in quasi-two-dimensional superconductors is expected to occur when the applied magnetic field crosses a certain critical value [S. L. Sondhi, S. M. Girvin, J. P. Carini, and D. Shahar, Rev. Mod. Phys. 69, 315 (1997); A. M. Goldman, Int. J. Mod. Phys. B 24, 4081 (2010)]. A fundamental question is whether this transition is due to the localization of Cooper pairs or due to the destruction of them. Here we address this question by studying the SIT in amorphous WSi. Transport measurements reveal the localization of Cooper pairs at a quantum critical field B1c (Bose insulator), with a product of the correlation length and dynamical exponents zν∼4/3 near the quantum critical point. Beyond B1c, superconducting fluctuations still persist at finite temperatures. Above a second critical field B2c>B1c, the Cooper pairs are destroyed and the film becomes a Fermi insulator. The different phases all merge at a tricritical point at finite temperatures with zν=2/3. Our results suggest a sequential superconductor to Bose insulator to Fermi insulator phase transition, which differs from the conventional scenario involving a single quantum critical point.

Abstract

A zero-temperature magnetic-field-driven superconductor to insulator transition (SIT) in quasi-two-dimensional superconductors is expected to occur when the applied magnetic field crosses a certain critical value [S. L. Sondhi, S. M. Girvin, J. P. Carini, and D. Shahar, Rev. Mod. Phys. 69, 315 (1997); A. M. Goldman, Int. J. Mod. Phys. B 24, 4081 (2010)]. A fundamental question is whether this transition is due to the localization of Cooper pairs or due to the destruction of them. Here we address this question by studying the SIT in amorphous WSi. Transport measurements reveal the localization of Cooper pairs at a quantum critical field B1c (Bose insulator), with a product of the correlation length and dynamical exponents zν∼4/3 near the quantum critical point. Beyond B1c, superconducting fluctuations still persist at finite temperatures. Above a second critical field B2c>B1c, the Cooper pairs are destroyed and the film becomes a Fermi insulator. The different phases all merge at a tricritical point at finite temperatures with zν=2/3. Our results suggest a sequential superconductor to Bose insulator to Fermi insulator phase transition, which differs from the conventional scenario involving a single quantum critical point.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Electronic, Optical and Magnetic Materials
Physical Sciences > Condensed Matter Physics
Language:English
Date:29 June 2018
Deposited On:20 Dec 2018 12:14
Last Modified:29 Jul 2020 08:28
Publisher:American Physical Society
ISSN:2469-9950
OA Status:Green
Publisher DOI:https://doi.org/10.1103/physrevb.97.214524

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