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arXiv · 2106.04672

Nematic response revealed by coherent phonon oscillations in BaFe$_2$As$_2$

Min-Cheol Lee·Inho Kwak·Yeongseon Lee·Bumjoo Lee·Byung Cheol Park·Thomas Wolf·Tae Won Noh·Kyungwan Kim
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Abstract

We investigate coherent phonon oscillations of BaFe$_2$As$_2$ using optical pump-probe spectroscopy. Time-resolved optical reflectivity shows periodic modulations due to $A_{1g}$ coherent phonon of $c$-axis arsenic vibrations. Optical probe beams polarized along the orthorhombic $a$- and $b$-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 $c$-axis arsenic vibrations. The oscillation-phase remains anisotropic even in the tetragonal structure, reflecting a nematic response of BaFe$_2$As$_2$. 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.

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Min-Cheol Lee, Inho Kwak, Yeongseon Lee, Bumjoo Lee, Byung Cheol Park, Thomas Wolf, Tae Won Noh, Kyungwan Kim. 2021-06-08. Nematic response revealed by coherent phonon oscillations in BaFe$_2$As$_2$. https://doi.org/10.1103/physrevb.105.024501

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