TY - JOUR
T1 - Gate-controlled BCS-BEC crossover in a two-dimensional superconductor
AU - Nakagawa, Yuji
AU - Kasahara, Yuichi
AU - Nomoto, Takuya
AU - Arita, Ryotaro
AU - Nojima, Tsutomu
AU - Iwasa, Yoshihiro
N1 - Funding Information:
Supported by A3 Foresight Program and JSPS KAKENHI grants JP19H05602 and JP17J08941. Y.N. was supported by the Materials Education Program for the Future Leaders in Research, Industry, and Technology (MERIT).
Publisher Copyright:
© 2021 American Association for the Advancement of Science. All rights reserved.
PY - 2021/4/9
Y1 - 2021/4/9
N2 - Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC) are the two extreme limits of the ground state of the paired fermion systems. We report crossover behavior from the BCS limit to the BEC limit realized by varying carrier density in a two-dimensional superconductor, electron-doped zirconium nitride chloride. The phase diagram, established by simultaneous measurements of resistivity and tunneling spectra under ionic gating, demonstrates a pseudogap phase in the low-doping regime. The ratio of the superconducting transition temperature and Fermi temperature in the low-carrier density limit is consistent with the theoretical upper bound expected in the BCS-BEC crossover regime. These results indicate that the gate-doped semiconductor provides an ideal platform for the two-dimensional BCS-BEC crossover without added complexities present in other solid-state systems.
AB - Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC) are the two extreme limits of the ground state of the paired fermion systems. We report crossover behavior from the BCS limit to the BEC limit realized by varying carrier density in a two-dimensional superconductor, electron-doped zirconium nitride chloride. The phase diagram, established by simultaneous measurements of resistivity and tunneling spectra under ionic gating, demonstrates a pseudogap phase in the low-doping regime. The ratio of the superconducting transition temperature and Fermi temperature in the low-carrier density limit is consistent with the theoretical upper bound expected in the BCS-BEC crossover regime. These results indicate that the gate-doped semiconductor provides an ideal platform for the two-dimensional BCS-BEC crossover without added complexities present in other solid-state systems.
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U2 - 10.1126/science.abb9860originally
DO - 10.1126/science.abb9860originally
M3 - Article
C2 - 33737401
AN - SCOPUS:85104159754
VL - 372
SP - 190
EP - 195
JO - Science
JF - Science
SN - 0036-8075
IS - 6538
ER -