Reutzel Marcel, Li Andi, Wang Zehua, Petek Hrvoje
Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, 15260, USA.
I. Physikalisches Institut, Georg-August-Universität Göttingen, Göttingen, Germany.
Nat Commun. 2020 May 6;11(1):2230. doi: 10.1038/s41467-020-16064-4.
Depending on the applied strength, electromagnetic fields in electronic materials can induce dipole transitions between eigenstates or distort the Coulomb potentials that define them. Between the two regimes, they can also modify the electronic properties in more subtle ways when electron motion becomes governed by time and space-periodic potentials. The optical field introduces new virtual bands through Floquet engineering that under resonant conditions interacts strongly with the preexisting bands. Under such conditions the virtual bands can become real, and real ones become virtual as the optical fields and electronic band dispersions entangle the electronic response. We reveal optical dressing of electronic bands in a metal by exciting four-photon photoemission from the Cu(111) surface involving a three-photon resonant transition from the Shockley surface band to the first image potential band. Attosecond resolved interferometric scanning between identical pump-probe pulses and its Fourier analysis reveal how the optical field modifies the electronic properties of a solid through combined action of dipole excitation and field dressing.
根据所施加的强度，电子材料中的电磁场可诱导本征态之间的偶极跃迁，或使定义这些本征态的库仑势发生畸变。在这两种情况之间，当电子运动由时间和空间周期势支配时，它们还能以更微妙的方式改变电子特性。光场通过弗洛凯工程引入新的虚拟能带，在共振条件下，这些虚拟能带与已有的能带强烈相互作用。在这种条件下，虚拟能带可以变为真实能带，而真实能带则变为虚拟能带，因为光场和电子能带色散会使电子响应相互纠缠。我们通过激发来自Cu(111)表面的四光子光电子发射揭示了金属中电子能带的光学修饰，其中涉及从肖克利表面能带到第一镜像势能带的三光子共振跃迁。相同泵浦 - 探测脉冲之间的阿秒分辨干涉扫描及其傅里叶分析揭示了光场如何通过偶极激发和场修饰的联合作用来改变固体的电子特性。
