title: Ab initio simulation of electrical currents induced by ultrafast laser excitation of dielectric materials.
abstract: We theoretically investigate the generation of ultrafast currents in insulators induced by strong few-cycle laser pulses. Ab initio simulations based on time-dependent density functional theory give insight into the atomic-scale properties of the induced current signifying a femtosecond-scale insulator-metal transition. We observe the transition from nonlinear polarization currents during the laser pulse at low intensities to tunnelinglike excitation into the conduction band at higher laser intensities. At high intensities, the current persists after the conclusion of the laser pulse considered to be the precursor of the dielectric breakdown on the femtosecond scale. We show that the transferred charge sensitively depends on the orientation of the polarization axis relative to the crystal axis, suggesting that the induced charge separation reflects the anisotropic electronic structure. We find good agreement with very recent experimental data on the intensity and carrier-envelope phase dependence [A. Schiffrin et al., Nature (London) 493, 70 (2013).
authors.affiliation: Institute for Theoretical Physics, Vienna University of Technology, 1040 Vienna, Austria, EU.
authors.forename: Georg
authors.initials: G
authors.lastname: Wachter
authors.affiliation: Institute for Theoretical Physics, Vienna University of Technology, 1040 Vienna, Austria, EU.
authors.forename: Christoph
authors.initials: C
authors.lastname: Lemell
authors.affiliation: Institute for Theoretical Physics, Vienna University of Technology, 1040 Vienna, Austria, EU.
authors.forename: Joachim
authors.initials: J
authors.lastname: Burgdörfer
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
authors.forename: Shunsuke A
authors.initials: SA
authors.lastname: Sato
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan and Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan.
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Tong
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan and Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yabana