标题： 辐射诱导的狄拉克哈密顿量中弗洛凯-布洛赫能带的动力学形成 显示英文标题

标题： Radiation-induced dynamical formation of Floquet-Bloch bands in Dirac Hamiltonians

摘要： 最近的实验，将超快强场照射表面与时间-角度分辨光电子能谱相结合，使得能够监测时间依赖的载流子动力学以及由于辐射脉冲引起的瞬态侧带的形成。 尽管这些结构类似于弗洛凯-布洛赫带，但标准的弗洛凯理论不适用，因为它需要严格的时间周期驱动场。 为了研究这种侧带的出现和形成，即在常见弗洛凯物理与短脉冲驱动的动态机制之间建立联系，我们考虑了弗洛凯理论的一个推广，即所谓的$t-t^{\prime}$形式。 这种方法自然地将弗洛凯理论扩展到具有叠加包络形状的驱动场振幅。 受实验启发，我们研究了二维狄拉克哈密顿量，在线性偏振和圆偏振光波作用下，具有几周期高斯场包络的情况。 对于这些弗洛凯-布洛赫哈密顿量，我们研究了它们的弗洛凯-布洛赫谱的演化，并伴随对时间依赖（侧带）跃迁的系统分析。 我们表明，对于像石墨烯这样的线性狄拉克系统，侧带占据需要圆偏振光，而对于描述拓扑绝缘体表面态如 Bi$_2$ Se$_3$的具有三重扭曲的狄拉克模型，线性和圆偏振脉冲都会引起侧带激发。 显示英文摘要

摘要： Recent experiments, combing ultrafast strong-field irradiation of surfaces with time- and angle-resolved photoemission spectroscopy, allow for monitoring the time-dependent charge carrier dynamics and the build-up of transient sidebands due to the radiation pulses. While these structures are reminiscent of Floquet-Bloch bands, standard Floquet theory is not applicable since it requires a strictly time-periodic driving field. To study the emergence and formation of such sidebands, i.e. to provide a link between common Floquet physics and dynamical mechanisms underlying short driving pulses, we consider a generalization of Floquet theory, the so-called $t-t^{\prime}$ formalism. This approach naturally extents Floquet theory to driving field amplitudes with a superimposed envelope shape. Motivated by experiments we study 2D Dirac Hamiltonians subject to linearly and circularly polarised light waves with a Gaussian field envelope of a few cycles. For these Floquet-Bloch Hamiltonians we study the evolution of their Floquet-Bloch spectra, accompanied by a systematic analysis of the time-dependent (sideband) transitions. We show that sideband occupation requires circularly polarized light for linear Dirac systems such as graphene, while for Dirac models with trigonal warping, describing surface states of topological insulators such as Bi$_2$ Se$_3$, both linearly and circularly polarised pulses induce sideband excitations.