Limits...
Coupling and electrical control of structural, orbital and magnetic orders in perovskites.

Varignon J, Bristowe NC, Bousquet E, Ghosez P - Sci Rep (2015)

Bottom Line: Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials.Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations.The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity.

View Article: PubMed Central - PubMed

Affiliation: Physique Théorique des Matériaux, Université de Liège (B5), B-4000 Liège, Belgium.

ABSTRACT
Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials. The key to the functional electronic properties exhibited by perovskites is often the so-called Jahn-Teller distortion. For applications, an electrical control of the Jahn-Teller distortions, which is so far out of reach, would therefore be highly desirable. Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations. The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity. Thanks to the intimate coupling between Jahn-Teller distortions and electronic degrees of freedom, the electric field control of Jahn-Teller distortions is of general relevance and may find broad interest in various functional devices.

No MeSH data available.


Related in: MedlinePlus

Energy gains (in meV) by condensing various amplitudes of the individual ,  and Pz distortions.Potentials are plotted for a ‘↑’ (open blue symbols) and a ‘↓’ (filled blue symbols) initial electronic polarization.
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f4: Energy gains (in meV) by condensing various amplitudes of the individual , and Pz distortions.Potentials are plotted for a ‘↑’ (open blue symbols) and a ‘↓’ (filled blue symbols) initial electronic polarization.

Mentions: To understand the nature of their appearance, we plot in Fig. 4 each potential as a function of the distortion amplitude. All potentials present single wells, more or less shifted through an improper coupling with the electronic instability. This confirms that the electronic instability is the primary order parameter driving the phase transition. Moreover, the motion presents an energy gain of one to two orders of magnitude larger than those of the motion, indicating that the couples more strongly with the electronic instability, which might be expected. Consequently, once the electronic instability condenses, the lattice distortion is forced into the system which consequently produces the lattice part of the polarization through the structural hybrid improper coupling. This Jahn-Teller induced ferroelectricity amplifies by one order of magnitude the electronic out-of-plane polarization. The sign of the three lattice distortions is again imposed by the initial sign (up or down) of the electronic polarization. Consequently, the reversal of Pz through an application of an external electric field would require the reversal of both , and the magnitude of the magnetic moment of both VO2 planes. The saddle point at the midway of this reversal (all three modes equal zero, i.e. the Pb21m phase) is of the order of 10 meV higher in energy, which represents a reasonable estimate of the ferroelectric switching barrier. Compared to the rotationally driven ferroelectricity Pxy, whose energy barrier is of the order of 0.1 to 1 eV121415, this Jahn-Teller induced ferroelectricity is therefore very likely to be switchable. The large difference between the two energy barriers is due to two different energy landscapes involving i) the robust AFD motions inducing Pxy and ii) the relatively soft distortions inducing Pz.


Coupling and electrical control of structural, orbital and magnetic orders in perovskites.

Varignon J, Bristowe NC, Bousquet E, Ghosez P - Sci Rep (2015)

Energy gains (in meV) by condensing various amplitudes of the individual ,  and Pz distortions.Potentials are plotted for a ‘↑’ (open blue symbols) and a ‘↓’ (filled blue symbols) initial electronic polarization.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4612717&req=5

f4: Energy gains (in meV) by condensing various amplitudes of the individual , and Pz distortions.Potentials are plotted for a ‘↑’ (open blue symbols) and a ‘↓’ (filled blue symbols) initial electronic polarization.
Mentions: To understand the nature of their appearance, we plot in Fig. 4 each potential as a function of the distortion amplitude. All potentials present single wells, more or less shifted through an improper coupling with the electronic instability. This confirms that the electronic instability is the primary order parameter driving the phase transition. Moreover, the motion presents an energy gain of one to two orders of magnitude larger than those of the motion, indicating that the couples more strongly with the electronic instability, which might be expected. Consequently, once the electronic instability condenses, the lattice distortion is forced into the system which consequently produces the lattice part of the polarization through the structural hybrid improper coupling. This Jahn-Teller induced ferroelectricity amplifies by one order of magnitude the electronic out-of-plane polarization. The sign of the three lattice distortions is again imposed by the initial sign (up or down) of the electronic polarization. Consequently, the reversal of Pz through an application of an external electric field would require the reversal of both , and the magnitude of the magnetic moment of both VO2 planes. The saddle point at the midway of this reversal (all three modes equal zero, i.e. the Pb21m phase) is of the order of 10 meV higher in energy, which represents a reasonable estimate of the ferroelectric switching barrier. Compared to the rotationally driven ferroelectricity Pxy, whose energy barrier is of the order of 0.1 to 1 eV121415, this Jahn-Teller induced ferroelectricity is therefore very likely to be switchable. The large difference between the two energy barriers is due to two different energy landscapes involving i) the robust AFD motions inducing Pxy and ii) the relatively soft distortions inducing Pz.

Bottom Line: Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials.Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations.The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity.

View Article: PubMed Central - PubMed

Affiliation: Physique Théorique des Matériaux, Université de Liège (B5), B-4000 Liège, Belgium.

ABSTRACT
Perovskite oxides are already widely used in industry and have huge potential for novel device applications thanks to the rich physical behaviour displayed in these materials. The key to the functional electronic properties exhibited by perovskites is often the so-called Jahn-Teller distortion. For applications, an electrical control of the Jahn-Teller distortions, which is so far out of reach, would therefore be highly desirable. Based on universal symmetry arguments, we determine new lattice mode couplings that can provide exactly this paradigm, and exemplify the effect from first-principles calculations. The proposed mechanism is completely general, however for illustrative purposes, we demonstrate the concept on vanadium based perovskites where we reveal an unprecedented orbital ordering and Jahn-Teller induced ferroelectricity. Thanks to the intimate coupling between Jahn-Teller distortions and electronic degrees of freedom, the electric field control of Jahn-Teller distortions is of general relevance and may find broad interest in various functional devices.

No MeSH data available.


Related in: MedlinePlus