论文标题
超电流注射下的超导NBN中的非雷神terahertz第二次谐波产生
Nonreciprocal Terahertz Second Harmonic Generation in Superconducting NbN under Supercurrent Injection
论文作者
论文摘要
在Terahertz（Thz）（THZ）频率范围的巨型第二次谐波一代（SHG）在S-Wave超导体NBN的薄膜中观察到，其中时间逆转（$ \ Mathcal {t} $ - ）和太空变为（$ \ Mathcal {p} $ - - symmeTrie symmeTrie symulties symulties aigntion symulties auncection takection。我们证明，当超电流的方向倒置时，第二谐波（SH）信号的相位会翻转，即，信号归因于损坏的$ \ MATHCAL {P} $ - 和$ \ MATHCAL {T} $ SYMMETRIES下发生的非转向响应。 SH信号的温度依赖性表现出鲜明的共振，这是由THZ电场在非旋转电势中驱动的涡流运动所解释的。最大转化率$η_{\ Mathrm {shg}} $在薄膜NBN中达到$ \ oft10^{ - 2} $，在场上冷却后的厚度为25 nm，磁场的厚度为25 nm，非常小的$ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ y的，为$ \ oe \ oe。
Giant second-harmonic generation (SHG) in the terahertz (THz) frequency range is observed in a thin film of an s-wave superconductor NbN, where the time-reversal ($\mathcal{T}$-) and space-inversion ($\mathcal{P}$-) symmetries are simultaneously broken by supercurrent injection. We demonstrate that the phase of the second-harmonic (SH) signal flips when the direction of supercurrent is inverted, i.e., the signal is ascribed to the nonreciprocal response that occurs under broken $\mathcal{P}$- and $\mathcal{T}$-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 $η_{\mathrm{SHG}}$ reaches $\approx10^{-2}$ in a thin film NbN with the thickness of 25 nm after the field cooling with a very small magnetic field of $\approx1$ Oe, for a relatively weak incident THz electric field of 2.8 kV/cm at 0.48 THz.
