High-Field Terahertz Bulk Photovoltaic Effect in Lithium Niobate

Abstract

The terahertz (THz) response of the ferroelectric prototype material lithium niobate (LiNbO3) is studied in the nonperturbative regime of light-matter interaction. Applying two-dimensional THz spectroscopy with few-cycle pulses of an amplitude E≈100 kV/cm and a center frequency of 2 THz, we dissect the overall nonlinear response into different orders in the electric field. The underlying nonlinear current is of interband character and consists of a strong low-frequency shift current (SC) and higher harmonics of the THz fundamental. The SC component originates from the lack of inversion symmetry and the strong interband decoherence for long electron trajectories in k space as shown by theoretical calculations.

Nonlinear terahertz coherent excitation of vibrational modes of liquids

“…Indeed, pioneering 2D THz work has been done on a variety of systems such as semiconductor quantum wells, 12,13 graphene, 14 and nonlinear crystals. 15 These techniques demonstrate the breadth of science that can be addressed with THz techniques.…”

First-Principles Materials Design of High-Performing Bulk Photovoltaics with theLiNbO3Structure

“…Despite intense initial interest, early explorations revealed low energy conversion efficiency, in part due to the high band gaps of most known ferroelectrics. Additionally, despite several proposed mechanisms, the physical origin of the BPVE was unclear [2,[5][6][7][8].However, recent emphasis on alternative energy technologies and the observation of the effect in novel semiconducting ferroelectrics (with band-gaps in the visible range) has renewed interest [9][10][11][12][13][14]. Several studies have attempted to elucidate the various contributions to the photovoltaic response -bulk or otherwise -in ferroelectrics [15][16][17][18][19][20][21][22][23].…”

Focus: Phase-resolved nonlinear terahertz spectroscopy—From charge dynamics in solids to molecular excitations in liquids

“…5,6,39,[80][81][82][83][84][85] Intersubband (IS) transitions in lowdimensional, in particular quasi-2D semiconductor nanostructures 5,6,80 as well as electronic interband transitions in the semiconductor InSb, 82,83 epitaxial multi-layer graphene, 39,84,85 and the ferroelectric material 81 LiNbO 3 were investigated. All 2D THz experiments on interband transitions were performed in the non-perturbative regime, where the strength of lightmatter interaction is comparable to or even larger than electronic couplings in the material.…”