Switchable photovoltaic response in hexagonal LuMnO3 single crystals

Hexagonal manganites, such as h-LuMnO3, are ferroelectric with its polar axis along the hexagonal axis and have a narrow electronic bandgap (≈ 1.5 eV). Using Pt electrodes, h LuMnO3 single crystals display a strong rectification, characteristic of a Schottky diode, and a large photoresponse. It is found that the short circuit photocurrent Jsc along the polar axis is modulated (up to 25 %) by the direction of the ferroelectric polarization P, leading to a short circuit photocurrent loop that mimics the ferroelectric polarization, and by polarization back switching. However, a non-switchable Jsc persists. Diffusion photocurrent is shown to dominate current-in-plane measurements and contributes to the non-switchable Jsc. This observation illustrates the dramatic role of the large optical absorption in hexagonal manganites. The accompanying optical dichroism shall challenge disentangling a genuine bulk photovoltaic response in h-LuMnO3 single crystal contributing to the non-switchable Jsc. Epitaxial thin films may offer a suitable alternative.Financial support from the Spanish Ministry of Science, Innovation and Universities, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (FUNFUTURE CEX2019-000917-S), MAT2017-85232-R (AEI/FEDER, EU), and PID2019-107727RB-I00 (MINECO/FEDER, EU) projects and from Generalitat de Catalunya (No. 2017 SGR 1377) is acknowledged. I.F. acknowledges RyC Contract No. RYC-2017-22531. Project supported by a 2020 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. Y.S is financially supported by China Scholarship Council (CSC) with No. 201806410010. The work of Y.S. has been done as a part of her Ph.D. program in Materials Science at Universitat Autònoma de Barcelona. A. Schankler and A. M. Rappe are acknowledged for the critical reading of the manuscript.Peer reviewe