Ultrafast Collective Dynamics in the Charge-Density-Wave Conductor K 0.3 MoO 3
Abstract
Low-energy coherent charge-density wave excitations are investigated in blue bronze (K
0.3
MoO
3
) and red bronze (K
0.33
MoO
3
) by femtosecond pump-probe spectroscopy. A linear gapless, acoustic-like dispersion relation is observed for the transverse phasons with a pronounced anisotropy in K
0.33
MoO
3
. The amplitude mode exhibits a weak (optic-like) dispersion relation with a frequency of 1.67 THz at 30 K. Our results show for the first time that the time-resolved optical technique provides momentum resolution of collective excitations in strongly correlated electron systems.Low-energy coherent charge-density wave excitations are investigated in blue bronze (K
0.3
MoO
3
) and red bronze (K
0.33
MoO
3
) by femtosecond pump-probe spectroscopy. A linear gapless, acoustic-like dispersion relation is observed for the transverse phasons with a pronounced anisotropy in K
0.33
MoO
3
. The amplitude mode exhibits a weak (optic-like) dispersion relation with a frequency of 1.67 THz at 30 K. Our results show for the first time that the time-resolved optical technique provides momentum resolution of collective excitations in strongly correlated electron systems.