Terahertz pulse-driven collective mode in the nematic superconducting state of Ba1−xKxFe2As2

We investigate the collective mode response of the iron-based superconductor Ba1−xKxFe2As2 using intense terahertz (THz) light. In the superconducting state a THz Kerr signal is observed and assigned to nonlinear THz coupling to superconducting degrees of freedom. The polarization dependence of the THz Kerr signal is remarkably sensitive to the coexistence of a nematic order. In the absence of nematic order the C4 symmetric polarization dependence of the THz Kerr signal is consistent with a coupling to the Higgs amplitude mode of the superconducting condensate. In the coexisting nematic and superconducting state the signal becomes purely nematic with a vanishing C4 symmetric component, signaling the emergence of a superconducting collective mode activated by nematicity.

A Contactless Liquor Level Detection Method Using Terahertz Time-Domain Spectroscopy

In this paper, we proposed the terahertz technique to measure the liquid level of Chinese liquor in sealed pots. We analyzed the transmission process of terahertz pulse in the sealed pots and established a model of the relationship between terahertz pulse interval and liquor level. The measurement results are in good agreement with the theoretical model. The results show that the terahertz technique can realize the high precision measurement of liquor level. The absolute and relative errors are less than ±40 μm and 0.014%, respectively. In addition, we also evaluated the influence of dewdrop on the measurement accuracy. The results show that dewdrop only leads to a deviation of 18 μm. The results prove the value of terahertz technology in the field of liquid level monitoring.