We propose a scheme for retrieving the ultrafast valley polarization (VP) dynamics in two-dimensional hexagonal materials via attosecond circular dichroism (CD) transient absorption spectroscopy. This approach builds on the CD transition between the first and higher conduction bands induced by the circularly polarized probe pulses. The population imbalance at nonequivalent valleys in the first conduction band is proportionally mapped onto the difference in absorption coefficients of two probe pulses with opposite helicities, supporting an unprecedented quantitative retrieval of the corresponding VP dynamics with subfemtosecond time resolution. We theoretically demonstrate the scheme for $h$-BN and ${\mathrm{MoS}}_2$ through ab initio calculations, achieving an accurate retrieval of the VP dynamics, particularly the transient VP switching processes, with a time resolution of 250 as.

Close

PrevNext

View figure in article

• Ultrafast optics
• Ultrafast phenomena
• Valley degrees of freedom
• 2-dimensional systems
• Time-dependent DFT