Abstract
Attosecond transient absorption is an ultrafast technique that has opened the possibility to study electron dynamics in condensed matter systems at its natural timescale. The extension to the x-ray regime permits one to use this powerful technique in combination with the characteristic element specificity of x-ray spectroscopy. At these timescales, the coherent effects of the electron transport are essential and have a relevant signature on the absorption spectrum. Typically, the complex light-driven dynamics requires a theoretical modeling for shedding light on the time-dependent changes in the spectrum. Here we construct a semiconductor Bloch equation model for resolving the light-induced and core-electron dynamics simultaneously, which enables to easily disentangle the interband and intraband contributions. By using the Bloch model, we demonstrate a universal feature on attosecond x-ray transient absorption spectra that emerges from the light-induced coherent intraband dynamics. This feature is linked to previous studies of light-induced Fano resonances in atomic systems.
Highlights
The revolution of producing pulses as short as several attoseconds (10−18 s) has opened the door of observing the fast motion of electron in complex systems and exploring a new quantum realm at unprecedented time scales
Attosecond transient absorption (ATA) has been successfully applied to studies of electron dynamics in material systems, allowing to understand petahertz conductivity changes in dielectrics [1], tunneling excitation induced by intense laser pulses [2], sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials [3], among other interesting ultrafast studies [4,5,6,7,8]
2.3. core-stateresolved Bloch equations (cBE) theory as time-dependent configuration interaction singles (TD-CIS) The derivation of the semiconductor Bloch equations (SBE) and cBE theory is based on creation and annihilation operators and is different from other many-body approaches used in condensed-matter systems to calculate the electronic properties
Summary
The revolution of producing pulses as short as several attoseconds (10−18 s) has opened the door of observing the fast motion of electron in complex systems and exploring a new quantum realm at unprecedented time scales. Semiconductor Bloch equations (SBE) [14,15,16,17] have been successfully applied to describe the nonlinear response of semiconductors and two-dimensional materials under the interaction of intense IR and mid-IR laser pulses [18,19,20,21,22,23], and to model ultrafast studies [6] This many-body theory offers clear advantages for understanding and interpreting the induced complex dynamics, such as separating the intraband and interband contribution as well as reducing the numerical effort. We discuss the importance of this effect on ultrafast studies with mid-IR wavelengths or physical systems with high conductivity properties
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