TY - JOUR
T1 - Nonreciprocal Terahertz Second-Harmonic Generation in Superconducting NbN under Supercurrent Injection
AU - Nakamura, Sachiko
AU - Katsumi, Kota
AU - Terai, Hirotaka
AU - Shimano, Ryo
N1 - Publisher Copyright:
© 2020 American Physical Society.
PY - 2020/8/28
Y1 - 2020/8/28
N2 - Giant second-harmonic generation in the terahertz (THz) frequency range is observed in a thin film of an s-wave superconductor NbN, where the time-reversal (T) and space-inversion (P) symmetries are simultaneously broken by supercurrent injection. We demonstrate that the phase of the second-harmonic signal flips when the direction of supercurrent is inverted; i.e., the signal is ascribed to the nonreciprocal response that occurs under broken P and T symmetries. The temperature dependence of the SH signal exhibits a sharp resonance, which is accounted for by the vortex motion driven by the THz electric field in an anharmonic pinning potential. The maximum conversion ratio ηSHG reaches ≈10-2 in a thin film NbN with the thickness of 25 nm after the field cooling with a very small magnetic field of ≈1 Oe, for a relatively weak incident THz electric field of 2.8 kV/cm at 0.48 THz.
AB - Giant second-harmonic generation in the terahertz (THz) frequency range is observed in a thin film of an s-wave superconductor NbN, where the time-reversal (T) and space-inversion (P) symmetries are simultaneously broken by supercurrent injection. We demonstrate that the phase of the second-harmonic signal flips when the direction of supercurrent is inverted; i.e., the signal is ascribed to the nonreciprocal response that occurs under broken P and T symmetries. The temperature dependence of the SH signal exhibits a sharp resonance, which is accounted for by the vortex motion driven by the THz electric field in an anharmonic pinning potential. The maximum conversion ratio ηSHG reaches ≈10-2 in a thin film NbN with the thickness of 25 nm after the field cooling with a very small magnetic field of ≈1 Oe, for a relatively weak incident THz electric field of 2.8 kV/cm at 0.48 THz.
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U2 - 10.1103/PhysRevLett.125.097004
DO - 10.1103/PhysRevLett.125.097004
M3 - Article
C2 - 32915589
AN - SCOPUS:85090911764
SN - 0031-9007
VL - 125
JO - Physical review letters
JF - Physical review letters
IS - 9
M1 - 097004
ER -