Hybridization Dynamics in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>CeCoIn</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> Revealed by Ultrafast Optical Spectroscopy
Yao‐Peng Liu, Yongjun Zhang, Jianjun Dong, H. Lee, Z. X. Wei, Weili Zhang, Changlin Chen, Huiqiu Yuan, Yi‐feng Yang, J. Qi
Abstract
We investigate the quasiparticle dynamics in the prototypical heavy fermion ${\mathrm{CeCoIn}}_{5}$ using ultrafast optical pump-probe spectroscopy. Our results indicate that this material system undergoes hybridization fluctuations before the establishment of heavy electron coherence, as the temperature decreases from $\ensuremath{\sim}120\text{ }\text{ }\mathrm{K}$ (${T}^{\ifmmode\dagger\else\textdagger\fi{}}$) to $\ensuremath{\sim}55\text{ }\text{ }\mathrm{K}$ (${T}^{*}$). We reveal that the anomalous coherent phonon softening and damping reduction below ${T}^{*}$ are directly associated with the emergence of collective hybridization. We also discover a distinct collective mode with an energy of $\ensuremath{\sim}8\text{ }\text{ }\mathrm{meV}$, which may be experimental evidence of the predicted unconventional density wave. Our findings provide important information for understanding the hybridization dynamics in heavy fermion systems.