Xu Long, Tutunnikov Ilia, Gershnabel Erez, Prior Yehiam, Averbukh Ilya Sh
AMOS and Department of Chemical and Biological Physics, The Weizmann Institute of Science, Rehovot 7610001, Israel.
Phys Rev Lett. 2020 Jul 3;125(1):013201. doi: 10.1103/PhysRevLett.125.013201.
We present a novel, previously unreported phenomenon appearing in a thermal gas of nonlinear polar molecules excited by a single THz pulse. We find that the induced orientation lasts long after the excitation pulse is over. In the case of symmetric-top molecules, the time-averaged orientation remains indefinitely constant, whereas in the case of asymmetric-top molecules the orientation persists for a long time after the end of the pulse. We discuss the underlying mechanism, study its nonmonotonous temperature and amplitude dependencies, and show that there exist optimal parameters for maximal residual orientation. The persistent orientation implies a long-lasting macroscopic dipole moment, which may be probed by even harmonic generation and may enable deflection by inhomogeneous electrostatic fields.
我们展示了一种出现在由单个太赫兹脉冲激发的非线性极性分子热气体中的新颖的、此前未报道过的现象。我们发现，在激发脉冲结束后，诱导取向仍会持续很长时间。对于对称陀螺分子，时间平均取向会无限期保持恒定，而对于非对称陀螺分子，在脉冲结束后取向会持续很长时间。我们讨论了其潜在机制，研究了其非单调的温度和振幅依赖性，并表明存在实现最大残余取向的最佳参数。持续取向意味着存在持久的宏观偶极矩，这可以通过偶次谐波产生来探测，并且可能会在非均匀静电场中发生偏转。
