All-Optically Induced Ultrafast Photocurrents: Beyond the Instantaneous Coherent Response

Abstract

It is demonstrated that the noninstantaneous response of the optically induced coherent polarization tremendously influences the real-space shift of electronic charges in semiconductors. The possibility of coherently controlling this real-space shift with temporally nonoverlapping excitation pulses allows for the observation of a new type of shift current, which only exists for certain polarization-shaped excitation pulses and vanishes in the continuous-wave limit. In contrast to previously studied shift currents, the new current requires a phase mismatch between two orthogonal transition dipole moments and leads, within a nonlinear second-order description, to a tensor which is antisymmetric with respect to the order of the two exciting electric field amplitudes. These observations, which can even be made at room temperature and are expected to occur in a variety of semiconductor crystal classes, contribute to a better understanding of light-matter interaction involving degenerate bands. Thus, they are expected to prove important for future studies of coherent and nonlinear optical effects in semiconductors.

Ultrafast photocurrents at the surface of the three-dimensional topological insulator Bi2Se3

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Coherent control of ultrafast photocurrents using polarization-shaped optical pulses

“…The TI waists can be explaine resulting from excitation of the lh dependence) and from continuu cos(ω c τ) dependence) [1]. While at small |τ SSC dominates, at large |τ| the lhX SSC be due to the slower dephasing rate of lhXs continuum carriers.…”

“…In this work, we report a new type of shif antisymmetric response tensor using po optical excitation pulses whose linear pol rotates in time [1]. Such polarization shapes a two orthogonally polarized and temporally pulses.…”

Coherent Terahertz Control of Vertical Transport in Semiconductor Heterostructures

“…The ultrafast optical generation of photocurrents has attracted considerable attention over the past few years [1][2][3][4][5]. Using a coherent control scheme of two short coherent light pulses with central frequencies m and a>/2, it has been possible to induce electric currents not only in semiconductors but also on metal surfaces where ultrafast dephasing processes are omnipresent [6].…”