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arXiv · 2210.14053

Terahertz ionic Kerr effect: Two-phonon contribution to the nonlinear optical response in insulators

Martina Basini·Mattia Udina·Matteo Pancaldi·Vivek Unikandanunni·Stefano Bonetti·Lara Benfatto
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Abstract

The THz Kerr effect measures the birefringence induced in an otherwise isotropic material by a strong THz pulse driving the Raman-active excitations of the systems. Here we provide experimental evidence of a sizable Kerr response in insulating SrTiO3 due to infrared-active lattice vibrations. Such a signal, named ionic Kerr effect, is associated with the simultaneous excitation of multiple phonons. Thanks to a theoretical modeling of the time, polarization and temperature dependence of the birefringence we can disentangle the ionic Kerr effect from the off-resonant electronic excitations, providing an alternative tunable mechanism to modulate the refractive index on ultrashort time-scales via infra-red active phonons.

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Martina Basini, Mattia Udina, Matteo Pancaldi, Vivek Unikandanunni, Stefano Bonetti, Lara Benfatto. 2022-10-25. Terahertz ionic Kerr effect: Two-phonon contribution to the nonlinear optical response in insulators. https://doi.org/10.1103/physrevb.109.024309

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