Electric Field Control of Jahn-Teller Distortions in Bulk Perovskites

Abstract

The Jahn-Teller distortion, by its very nature, is often at the heart of the various electronic properties displayed by perovskites and related materials. Despite the Jahn-Teller mode being nonpolar, we devise and demonstrate, in the present Letter, an electric field control of Jahn-Teller distortions in bulk perovskites. The electric field control is enabled through an anharmonic lattice mode coupling between the Jahn-Teller distortion and a polar mode. We confirm this coupling and quantify it through first-principles calculations. The coupling will always exist within the Pb2 1 m space group, which is found to be the favored ground state for various perovskites under sufficient tensile epitaxial strain. Intriguingly, the calculations reveal that this mechanism is not only restricted to Jahn-Teller active systems, promising a general route to tune or induce novel electronic functionality in perovskites as a whole. DOI: 10.1103/PhysRevLett.116.057602 Perovskite ABO 3 compounds, and related materials, are fascinating systems exhibiting a diverse collection of properties, including ferroelectricity, magnetism, orbitalordering, metal-insulator phase transitions, superconductivity, and thermoelectricity [1]. Despite the wide range of physical behavior, a common point at the origin of many of them can be identified as being the Jahn-Teller (JT) distortion [2,3]. The Jahn-Teller distortion is, itself, intimately linked to electronic degrees of freedom, since, traditionally, it manifests to remove an electronic degeneracy, opening a band gap and favoring a particular orbital ordering which, in turn, can affect magnetic ordering. Furthermore, it plays an important role, for example, in colossal magnetoresistance phenomena in doped manganites [4], superconductivity [5,6], or the strong electronic correlation observed in the thermoelectric NaCoO 2 family [7].It would be highly desirable, for device functionality, for example, to be able to tune the Jahn-Teller distortion and, hence, its corresponding electronic properties, with the application of an external electric field. However, JahnTeller distortions are nonpolar and, hence, not directly tunable with an electric field.Recently, the concept of "hybrid improper ferroelectricity" has emerged within the community of oxide perovskites [8][9][10][11]. This concept is related to an unusual coupling of lattice modes, giving rise in the free energy expansion to a trilinear term −λPR 1 R 2 linking the polar motion P to two independent nonpolar distortions R 1 and R 2 . Such a coupling was identified in various layered perovskites [8,9,[12][13][14][15], metal-organic framework [16,17], and can even appear in bulk ABO 3 perovskites [18,19]. Interestingly, in Ruddlesden-Popper compounds [9,20] and ABO 3 =A 0 BO 3 superlattices [21], this trilinear coupling appeared as a practical way to achieve electric control of nonpolar antiferrodistortive (AFD) motions associated with the rotation of the oxygen octahedra (i.e., monitoring P with an electric field will directly and sizeably...

Charge-Order-Induced Ferroelectricity inLaVO3/SrVO3Superlattices

“…1(a), we first observe that with average valence +3.5, the vanadium ions are expected to disproportionate to V 3+ and V 4+ . Each valence state drives a corresponding Jahn-Teller distortion of its coordinating oxygen octahedron [25,26]. As shown in Fig.…”

Dynamics of antipolar distortions

“…Examples of these two latter quantities are two different oxygen octahedral tiltings, [1][2][3][4][5][6][7] one oxygen octahedral tiling and one antipolar motion, 8 one Jahn-Teller mode and one antiferrodistortive (or antipolar) distortion, 9,10 or even two pseudo-Jahn-Teller motions. 11 Note also that trilinear energetic couplings do not restrain themselves to polar materials since they can also arise in compounds possessing antipolar cation distortions via their couplings with antiphase and inphase octahedral tiltings.…”

Pressure‐Induced Multiferroics via Pseudo Jahn–Teller Effects and Novel Couplings

“…It is rather the so-called K 3 mode, which consists of a tilt of the oxygen bipyramid and buckling of the R layers, and which generates a polarization via a 3 3 Q P K energetic coupling [23] (interestingly, in these hexagonal systems the magnitude of the polarization increases with hydrostatic pressure, [22,39] which contrasts with the present behavior shown in Figure 2b). Furthermore, some recent computational works also predict that polarization can couple with JT distortions, [17,18] but in such cases the polarization is the primary order parameter and couples with the JT modes via anharmonic trilinear terms. Such a trilinear couplings involve, in addition to the polarization and JT distortion, a third mode (typically, a tilting of the oxygen octahedra, or some antipolar motions); this is in stark contrast with our present case, where the key coupling only involves two modes, X 2 and 2 Γ − .…”

“…This discovery should be of high interest given, on one hand, the scarcity of multiferroic materials and, on the other hand, the technological promise of materials with JT distortions and electronic properties tunable by application of electric fields. [17][18][19][20][21] …”

“…More precisely, we discover that applying pressure to many magnetic rare-earth manganites RMnO 3 not only leads to the stabilization of the post-postperovskite structure but also induces pseudo Jahn-Teller effects that, in turn, yield a spontaneous electrical polarization via a previously unknown coupling. Interestingly, the latter coupling only involves the polarization and the mentioned JT distortion; this feature sets the new coupling apart from other trilinear effects, [17,18] in which a third structural distortion appears, as it strongly suggests the possibility of an easier control of JT effects and related electronic properties via the application of Multiferroic materials are currently attracting a lot of interest because of the cross-coupling between their electrical and magnetic properties, which has the potential to lead to novel devices. There is a relatively small number of multiferroics and, hence, various strategies have been proposed to design materials possessing both ordered electric and magnetic dipoles.…”