Terahertz-driven phonon upconversion in SrTiO3

Direct manipulation of the atomic lattice using intense long-wavelength laser pulses has become a viable approach to create new states of matter in complex materials. Conventionally, a high-frequency vibrational mode is driven resonantly by a mid-infrared laser pulse and the lattice structure is mod...

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Bibliographic Details
Published in:Nature physics 2019-04, Vol.15 (4), p.387-392
Main Authors: Kozina, M., Fechner, M., Marsik, P., van Driel, T., Glownia, J. M., Bernhard, C., Radovic, M., Zhu, D., Bonetti, S., Staub, U., Hoffmann, M. C.
Format: Article
Language:English
Subjects:
639/766/119
639/766/119/996
639/766/400/1106
639/766/400/561
639/766/400/584
Anharmonicity
Atomic
ATOMIC AND MOLECULAR PHYSICS
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Coupling
Displacements (lattice)
Femtosecond pulses
Infrared lasers
Lasers
Lattice vibration
Mapping
MATERIALS SCIENCE
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Phase transitions
Phonons
Physics
Physics and Astronomy
Radiation
Strontium
Strontium titanates
Theoretical
Transition metal oxides
Transition metals
Upconversion
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Summary:Direct manipulation of the atomic lattice using intense long-wavelength laser pulses has become a viable approach to create new states of matter in complex materials. Conventionally, a high-frequency vibrational mode is driven resonantly by a mid-infrared laser pulse and the lattice structure is modified through indirect coupling of this infrared-active phonon to other, lower-frequency lattice modulations. Here, we drive the lowest-frequency optical phonon in the prototypical transition metal oxide SrTiO 3 well into the anharmonic regime with an intense terahertz field. We show that it is possible to transfer energy to higher-frequency phonon modes through nonlinear coupling. Our observations are carried out by directly mapping the lattice response to the coherent drive field with femtosecond X-ray pulses, enabling direct visualization of the atomic displacements. A spectroscopic study of strontium titanate provides a method for transferring the vibrational energy of a low-frequency phonon mode to higher-frequency modes, with the potential to access elusive ‘silent’ modes.
ISSN:1745-2473
1745-2481
DOI:10.1038/s41567-018-0408-1