@article{0e101034cc154d9bade6c19cff2daf8a,
title = "Abnormal phase flip in the coherent phonon oscillations of Ca2RuO4",
abstract = "We employ an optical pump-probe technique to study coherent phonon oscillations in Ca2RuO4. We find that oscillation amplitude of an Ag symmetric phonon mode is strongly suppressed at 260 K, a putative transition point of orbital ordering. The oscillation also shows a gradual but huge change in its phase, such that the oscillation even flips over with a 180 change across the temperature. Density functional theory calculations indicate that the Ag phonon has an eigenmode of octahedral distortion with conventional tilting along the a axis and antipolar distortion of apical oxygen. Careful inspection of the lattice captures an unusually large antipolar distortion in low-temperature structures, which may play a crucial role for the phase transition at 260 K.",
author = "Lee, {Min Cheol} and Kim, {Choong H.} and Inho Kwak and J. Kim and S. Yoon and Park, {Byung Cheol} and Bumjoo Lee and F. Nakamura and C. Sow and Y. Maeno and Noh, {T. W.} and Kim, {K. W.}",
note = "Funding Information: This work was supported by the Institute for Basic Science (IBS) in Korea (IBS-R009-D1). K.W.K. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF-2015R1A2A1A10056200 and 2017R1A4A1015564). J.K. and S.Y. were supported by NRF-2016R1D1A1B01009032. This work was supported by Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) (No. JP15H05852, No. JP15K21717, and No. JP17H06136), JSPS Core-to-Core program. C.S. acknowledges support of the JSPS International Research Fellowship (No. JP17F17027). Funding Information: This work was supported by the Institute for Basic Science (IBS) in Korea (IBS-R009-D1). K.W.K. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF-2015R1A2A1A10056200 and 2017R1A4A1015564). J.K. and S.Y. were supported by NRF-2016R1D1A1B01009032. This work was supported by Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) (No. JP15H05852, No. JP15K21717, and No. JP17H06136), JSPS Core-to-Core program. C.S. acknowledges support of the JSPS International Research Fellowship (No. JP17F17027). Publisher Copyright: {\textcopyright} 2018 American Physical Society.",
year = "2018",
month = oct,
day = "17",
doi = "10.1103/PhysRevB.98.161115",
language = "English",
volume = "98",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Physical Society",
number = "16",
}