title: Giant photovoltaic effects driven by residual polar field within unit-cell-scale LaAlO₃ films on SrTiO₃.
abstract: For polar/nonpolar heterostructures, Maxwell's theory dictates that the electric potential in the polar components will increase divergently with the film thickness. For LaAlO₃/SrTiO₃, a conceptually intriguing route, termed charge reconstruction, has been proposed to avert such "polar catastrophe". The existence of a polar potential in LaAlO₃ is a prerequisite for the validity of the charge reconstruction picture, yet to date, its direct measurement remains a major challenge. Here we establish unambiguously the existence of the residual polar potential in ultrathin LaAlO₃ films on SrTiO₃, using a novel photovoltaic device design as an effective probe. The measured lower bound of the residual polar potential is 1.0 V. Such a direct observation of the giant residual polar potential within the unit-cell-scale LaAlO₃ films amounts to a definitive experimental evidence for the charge reconstruction picture, and also points to new technological significance of oxide heterostructures in photovoltaic and sensing devices with atomic-scale control.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Haixing
authors.initials: H
authors.lastname: Liang
authors.forename: Long
authors.initials: L
authors.lastname: Cheng
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Zhai
authors.forename: Nan
authors.initials: N
authors.lastname: Pan
authors.forename: Hongli
authors.initials: H
authors.lastname: Guo
authors.forename: Jin
authors.initials: J
authors.lastname: Zhao
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wang
authors.forename: Changgan
authors.initials: C
authors.lastname: Zeng
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Zhang
authors.forename: J G
authors.initials: JG
authors.lastname: Hou