Injection current spectroscopy in magnetic Rashba semiconductor (Ge,Mn)Te by mid-infrared excitation

Toward the realization of a resilient society, photoelectric conversion has been constantly explored in order to use them as renewable energy sources. One scenario of photoelectric conversion strategy would be utilizing bulk photovoltaic effect in materials lacking inversion symmetry. One mechanism responsible for such photovoltaic effect is injection current, originating from asymmetric optical excitation at ± k points in the momentum space. Such excitations can be realized in a lifted band symmetry through the Zeeman effect on spin-split bands, or in the presence of Berry curvature dipole with a circular optical excitation. This nonlinear optical effect has attracted renewed attention due to its quantum geometric origin, i.e., Berry curvature as their source. To maximize the yield of photocurrent, now it is proposed to utilize the diverging geometric phases at the Dirac points. We employ thin films of GeTe with giant Rashba-type spin splitting doped with Mn. The Fermi level can be tuned near the Dirac point of the valence band by growth condition. Photocurrent spectroscopy in the mid-infrared region reveals that a large zero-bias photocurrent appears normal to the in-plane external magnetic field B, which reverses its sign upon the reversal of B, consistent with the selection rule of injection current. In this presentation, we will discuss the detailed spectral features with the possible effect of Berry curvature near the Fermi level.