Strain Driven Conducting Domain Walls in a Mott Insulator

Abstract

wide interfaces, for example, domain walls, have been reported to possess the same inherent electronic response as existing circuit elements, such as switches [6] and half-wave rectifiers. [7] In addition, ferroelectric domain walls can be reconfigured in situ by a variety of external fields which can lead to exotic bulk responses. Such bulk responses offer the opportunity to both enhance existing technology (e.g., magnetoresistance, [8] colossal dielectric constants, [9] memristive behavior [10] ) but also provide next generation functionality like, negative capacitance, [11] above band gap photovoltaic effects, [12] and domain wall nanoelectronics. [13] Such effects have been discussed from both a fundamental and a technological perspective in recent reviews. [14,15] For all of these bulk responses, the key requirement is for the domain walls to exhibit a different conductivity compared to the surrounding material. Therefore, much of the research has focused on ferroelectrics as the build up of screening charges at domain walls with polar discontinuities are known to modify the local conductivity. [13,14] Examples of this, in single crystals, include BaTiO 3 , [16] (Ca,Sr) 3 Ti 2 O 7 , [17] Cu-Cl boracite's, [18] LiNbO 3 , [19] h-RMnO 3 (R representing rare earth metals), [20] and GaV 4 S 8 . [8] Because of the energetically costly nature of such polar discontinuities, their spontaneous formations are normally restricted to improper ferroelectrics. [21,22] Indeed, so established is this screening charge mechanism that it is a surprise for an improper ferroelectric material, exhibiting polar discontinuities, not to have conducting domain walls. [23] In this scenario, the type of domain wall that is expected to have enhanced conductivity depends on the electronic structure of the host material: In a p-type (n-type) semiconductor the tail-to-tail (head-to-head) domain walls attract screening holes (electrons) and thus provide enhanced conductivity relative to the bulk. [24][25][26] The corresponding head-to-head (tail-to-tail) wall in a p-type (n-type) material is then expected to have reduced conductivity compared to the bulk. [13,21,22,27] Note, in ferroelectrics, particularly thin-films, further conductivity mechanisms have been reported. [6,[28][29][30][31][32] But it is challenging, especially in oxides, to disentangle intrinsic effects and those associated with, for example, enhanced defect density at domain walls, [33,34] which can change surface Schottky barriers and hence conductivity. [7] There have also been reports of domain wall conductivity and even superconductivity in non-ferroelectrics. Examples of the former case include, the antiferromagnetic insulators with conducting magnetic domain Rewritable nanoelectronics offer new perspectives and potential to both fundamental research and technological applications. Such interest has driven the research focus into conducting domain walls: pseudo-2D conducting channels that can be created, positioned, and deleted in situ. However, the study of conductive ...

Positive and Negative Pressure Regimes in Anisotropically Strained V2O3 Films

“…If the structural phase coexistence observed by XRD >200 K is indeed related to the PM/PI phase coexistence as suggested, it is expected that the local conductivity would vary significantly as observed in other material systems. [34][35][36][37] To test this, we measured conductive atomic force microscopy maps, which revealed large variations in current-voltage characteristics, attributed to PI and PM domains (see Figure 5). The maps reveal that PM/PI domains are elongated in the direction of the c-axis with a typical width of ≈100 nm.…”