910 research outputs found
Nematic response revealed by coherent phonon oscillations in BaFeAs
We investigate coherent phonon oscillations of BaFeAs using optical
pump-probe spectroscopy. Time-resolved optical reflectivity shows periodic
modulations due to coherent phonon of -axis arsenic vibrations.
Optical probe beams polarized along the orthorhombic - and -axes reveal
that the initial phase of coherent oscillations shows a systematic deviation as
a function of temperature, although these oscillations arise from the same
-axis arsenic vibrations. The oscillation-phase remains anisotropic even in
the tetragonal structure, reflecting a nematic response of BaFeAs. Our
study suggests that investigation on the phase of coherent phonon oscillations
in optical reflectivity can offer unique evidence of a nematic order strongly
coupled to a lattice instability.Comment: 5 pages, 4 figure
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