In strongly correlated oxides, heterointerfaces, manipulating the interaction, frustration, and discontinuity of lattice, charge, orbital, and spin degrees of freedom, generate new possibilities for next generation devices. In this study, existing oxide heterostructures are examined and local conduction at the BiFeO(3)-CoFe(2)O(4) vertical interface is found. In such hetero-nanostructures the interface cannot only be the medium for the coupling between phases, but also a new state of the matter. This study demonstrates a novel concept on for oxide interface design and opens an alternative pathway for the exploration of diverse functionalities in complex oxide interfaces.

Modulation of band bending at a complex oxide heterointerface by a ferroelectric layer is demonstrated. The as-grown polarization (Pup ) leads to charge depletion and consequently low conduction. Switching the polarization direction (Pdown ) results in charge accumulation and enhances the conduction at the interface. The metal-insulator transition at a conducting polar/nonpolar oxide heterointerface can be controlled by ferroelectric doping.

A new perovskite-like coordination polymer [(CH3)2NH2][Cd(N3)3] is reported which undergoes a reversible ferroelastic phase transition. This transition is due to varied modes of motion of the [(CH3)2NH2](+) guest accompanied by a synergistic deformation of the [Cd(N3)3](-) framework. The unusual two-staged switchable dielectric relaxation reveals the molecular dynamics of the polar cation guest, which are well controlled by the variable confined space of the host framework. As the material switches from the ferroelastic phase to the paraelastic phase, a remarkable increase of the rotational energy barrier is detected. As a result, upon heating at low temperature, this compound shows a notable change from a low to a high dielectric state in the ferroelastic phase. This thermoresponsive host-guest system may serve as a model compound for the development of sensitive thermoresponsive dielectric materials and may be key to understanding and modulating molecular/ionic dynamics of guest molecules in confined space.

In complex, correlated oxides, heterointerfaces have emerged as key focal points of current condensed matter science. [1][2][3] For ferroic oxides, in order to minimize the total energy, domain walls emerge as natural interfaces. Multiferroic materials show a wealth of controllable multiple ferroic order through stress, optical excitation, electric, or magnetic fi elds in the same phase, which in turn suggest potential applications in the realization of oxide-based electronic devices, such as spintronics, information storage devices, or communications. [4][5][6][7] According to the detailed classifi cation given by Mermin in ferroic systems, [ 8 ] domain walls in ferroic systems are considered as two dimensional (2D) topological defects, which play an important role in determining the functionality in materials with long-range order.Recently, several key studies pointed out interesting observations on domain walls in multiferroics. [9][10][11][12][13] For example, Y. Tokunaga et al. showed that ferroelectric polarization and magnetization are successfully controlled by magnetic and electric fi elds in GdFeO 3 , respectively, which is attributed to the unique feature of composite domain wall clamping. [ 14 ] T. Choi et al. observed insulating interlocked ferroelectric and structural antiphase domain walls in a multiferroic YMnO 3 system. [ 15 ] H. Bea et al. pointed out that domain walls are the source of the exchange bias interaction between the ferromagnetic metal layer and multiferroic BiFeO 3 (BFO). [ 16 ] Additionally, L. W. Martin further confi rmed that as-grown 109 ° domain walls in BFO thin fi lms are the contribution for uncompensated spins. [ 17 ] In addition to the above, a very recent work has established electrical conductivity at written multiferroic domain walls in BFO at room temperature, which opens up a pathway by which to manipulate domain walls for next generation nanoelectronics.Exploring details on electronic states of domain polarization reorientations is critical in oxide multiferroic materials. Theoretically, the consideration of the evolution of the polarization across the 109 ° domain walls exhibits a large potential step. The prediction correlates with the enhanced electrical conductivity due to the generation of a space-charge layer for screening the potential discontinuity in the region of the wall. [ 2 ] Experimentally, conductive atomic force microscopy (c-AFM) studies show the occurrence of electrical conduction at 109 ° domain walls within the limited spatial resolution of the experimental technigue. [ 3 ] In spite of the critical importance of these discoveries at such an oxide interface, there have been no effectively direct investigations of the intrinsic evolution of the electronic properties at regions of domain walls specifi cally within the nanoscale.In this work, we explore the subject by measuring the local electronic structure using scanning tunneling microscopy (STM) in a cross-sectional geometry. STM and scanning tunneling spectroscopy (STS) studies provide direct exp...

Photodriven dipole reordering of the intercalated organic molecules in halide perovskites has been suggested to be a critical degree of freedom, potentially affecting physical properties, device performance, and stability of hybrid perovskite-based optoelectronic devices. However, thus far a direct atomically resolved dipole mapping under device operation condition, that is, illumination, is lacking. Here, we map simultaneously the molecule dipole orientation pattern and the electrostatic potential with atomic resolution using photoexcited cross-sectional scanning tunneling microscopy and spectroscopy. Our experimental observations demonstrate that a photodriven molecule dipole reordering, initiated by a photoexcited separation of electron–hole pairs in spatially displaced orbitals, leads to a fundamental reshaping of the potential landscape in halide perovskites, creating separate one-dimensional transport channels for holes and electrons. We anticipate that analogous light-induced polarization order transitions occur in bulk and are at the origin of the extraordinary efficiencies of organometal halide perovskite-based solar cells as well as could reconcile apparently contradictory materials’ properties.