## 1 Introduction
At moderate IR intensities, there are two interfering pathways for photoelectrons to contribute to the central side band at \(N\hbar\omega_{\text{IR}}-\varepsilon_{0}\): photoelectrons excited by the \((N+1)\)-th harmonic via emission of one IR photon, and those excited by the \((N-1)\)-th harmonic via the absorption of one IR photon. Hence, the intensity of the side band depends on the relative phase between both quantum paths. Variation of the IR-EUV delay results in intensity oscillation of the central side band, with an oscillation frequency that is twice as large as that of the fundamental IR radiation (lower-right panel of Figure 1). Moreover, side-bandoscillations are shifted with respect to the maximum of the EUV pulse by a RABBITT delay \(\tau_{\text{RABBITT}}\). Note that, since side-band oscillation in a RABBITT experiment is determined by phase differences between two quantum pathways, which is a genuine quantum property, in contrast to streaking spectrograms, RABBITT spectrograms cannot be interpreted within a classical picture. Hence, for the RABBITT process, the correspondence principle is not directly applicable, and it is not a priori obvious that RABBITT delay \(\tau_{\text{RABBITT}}\) directly reveals photoemission time \(t_{\text{PE}}\). Therefore, an important question that arises is whether delays determined by RABBITT (\(\tau_{\text{RABBITT}}\)) and streaking (\(\tau_{\text{streaking}}\)) for solid-state photoemission agree with each other. Different quantum-interference pathways compared to the streaking case might influence the shift of the RABBITT side-band oscillations on the delay axis. For illustration, photoelectrons in a RABBITT experiment only move inside the material with kinetic energies corresponding to (\(N\)\(-\)1)-th or (\(N\)\(+\)1)-th harmonics, while oscillations at the \(N\)-th harmonic are evaluated. However, the kinetic energy distribution inside the material is zero around the \(N\)-th harmonic. In contrast, in the streaking case, electrons move inside the material with kinetic energy centered on the \(N\)-th harmonic. This consideration also raises the question of how delays determined by both techniques are related to each other. In the gas phase, [PERSON] et al. experimentally demonstrated delay agreement within an accuracy of tens of attoseconds, determined from streaking and RABBITT spectra for the photoionization of Ne and Ar atoms [31]. For more complex many-body systems like solids, experimental proof for the equivalence of both methods is still missing. For instance, transport of the electron from inside the solid to the surface substantially contributes to photoemission delay. Moreover, in a solid-surface photoemission experiment, the interaction region with EUV field and IR field, respectively, are spatially separated if the IR field is screened at the surface. Therefore, delay contributions from Coulomb-laser coupling (streaking) [24; 25] and continuum-continuum coupling (RABBITT) [6] do not occur if the IR field inside the solid can be neglected. Hence, conclusions from gas-phase experiments cannot be directly transferred to solids. The goal of this article is to numerically explore the similarities and differences in time delays obtained from RABBITT and streaking spectroscopy as applied to solid-state photoemission. Note, however, that this is a theoretical view on attosecond-time-resolved spectroscopy. In a streaking or RABBITT experiment, relative delays between different emission channels are usually measured. For the present investigation, such relative delays would make identification of the underlying physics more difficult to present and would not provide additional information. Time delays obtainable from both methods are compared in this article by solving the one-dimensional time-dependent Schrodinger equation (TDSE) for potential contributions that were successfully applied to explain experiment results in time-resolved photoemission from solid surfaces [10; 16].