Photovoltaic effect by soft phonon excitation

Abstract

Photodetection is an indispensable function of optoelectronic devices in modern communication and sensing systems. Contrary to the near-infrared/visible regions, the fast and sensitive photodetectors operated at room temperature for the far-infrared/terahertz regions are not well developed despite a possibly vast range of applications. The bulk photovoltaic effect (BPVE) in single-phase noncentrosymmetric materials based on the shift current mechanism enables less-dissipative energy conversion endowed with instantaneous responsivity owing to the quantum-mechanical geometric phase of electronic states. Nevertheless, the small-band-gap material for the low-energy BPVE inevitably suffers from the thermal noise due to the intrinsically high conductivity. Here, we demonstrate the shift current induced by soft-phonon excitations without creation of electron-hole pairs in the archetypal ferroelectric BaTiO3 by using the terahertz light, whose energy scale is three orders of magnitude smaller than the electronic band gap. At and above room temperature, we observe appreciable photocurrents caused by the soft-phonon excitation as large as that for electronic excitation and their strong phonon-mode dependence. The observed phonon-driven BPVE can be well accounted for by the shift current model considering the electron-phonon coupling in the displacement-type ferroelectrics as supported by the first-principles calculation. Our findings establish the efficient quantum BPVE arising from low-energy elementary excitations, suggesting the novel principle for the high-performance terahertz photodetectors.

25 pages, 8 figures

References in corpus (4)

• Topology and geometry under the nonlinear electromagnetic spotlight
• Evidence of a coupled electron-phonon liquid in NbGe${}_2$
• Floating zone furnace equipped with a high power laser of 1kW composed of five smart beams
• Shift current from electromagnon excitations in multiferroics

Cited by in corpus (9)

• Geometric aspects of nonlinear and nonequilibrium phenomena
• Effects of relaxation on photovoltaic effect and possibility of photocurrent within transparent region
• Magnetic parity violation and parity-time-reversal-symmetric magnets
• Effect of collective spin excitation on electronic transport in topological spin texture
• Direct current generation by dielectric loss in ferroelectrics
• Bulk photovoltaic effect in antiferromagnet: Role of collective spin dynamics
• Theory of shift heat current and its application to electron-phonon coupled systems
• Role of Ward-Takahashi identity in an electron-phonon coupled system -- Revisiting phonon shift current
• Axion dark matter detection via shift current