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Schlagwörter:
PACS numbers: 77.80.Fm, 78.20.Bh, 63.20.Ry, 78.47.J−
Zusammenfassung:
I propose a method for ultrafast switching of ferroelectric polarization using midinfrared pulses. This involves selectively exciting the highest frequency A1 phonon mode of a ferroelectric material with an intense midinfrared pulse. Large amplitude oscillations of this mode provides a unidirectional force to the lattice such that it displaces along the lowest frequency A1 phonon mode coordinate because of a nonlinear coupling of the type gQPQIR2 between the two modes. First-principles calculations show that this coupling is large in perovskite transition-metal oxide ferroelectrics, and the sign of the coupling is such that the lattice displaces in the switching direction. Furthermore, I find that the lowest frequency A1 mode has a large QP3 order anharmonicity, which causes a discontinuous switch of electric polarization as the pump amplitude is continuously increased.
