论文标题
通过ta2nise中的声子挤压介导的时间晶体行为理论5
Theory of time-crystalline behaviour mediated by phonon squeezing in Ta2NiSe5
论文作者
论文摘要
我们从理论上研究了通过光激励启动的光子时间晶状体行为，高于激发子绝缘子候选者的电子间隙$ \ rm {ta_2 ni se_5} $。我们表明，在电子光激发之后，电子 - 光子耦合导致非常规的挤压声子状态，其特征是声子波动的周期性振荡。挤压振荡导致光子时间结晶行为。光子时间晶体行为的关键特征是狭窄频带中反射率的扩增。该理论得到了$ \ rm {ta_2 ni se_5} $的实验结果的支持，其中带有短脉冲的光激发带来增强的Terahertz反射率，并具有预测的功能。我们用简化的哈密顿量来解释导致THZ扩增的关键机制，其有效性得到了Ab-Initio DFT计算的支持。我们的理论表明，泵送的$ \ rm {ta_2 ni se_5} $是增益介质，证明可以使用挤压的声子噪声来在THZ通信应用中创建THZ放大器。
We theoretically investigate photonic time-crystalline behaviour initiated by optical excitation above the electronic gap of the excitonic insulator candidate $\rm{Ta_2 Ni Se_5}$. We show that after electron photoexcitation, electron-phonon coupling leads to an unconventional squeezed phonon state, characterised by periodic oscillations of phonon fluctuations. Squeezing oscillations lead to photonic time crystalline behaviour. The key signature of the photonic time crystalline behaviour is THz amplification of reflectivity in a narrow frequency band. The theory is supported by experimental results on $\rm{Ta_2 Ni Se_5}$ where photoexcitation with short pulses leads to enhanced terahertz reflectivity with the predicted features. We explain the key mechanism leading to THz amplification in terms of a simplified Hamiltonian whose validity is supported by ab-initio DFT calculations. Our theory suggests that the pumped $\rm{Ta_2 Ni Se_5}$ is a gain medium, demonstrating that squeezed phonon noise may be used to create THz amplifiers in THz communication applications.
