Extended Data Fig. 1: Fast hot-carrier relaxation in FLG.
From: Terahertz phonon engineering with van der Waals heterostructures
a, A near-infrared (NIR) pump-probe spectrum measured in an hBN/WSe2/hBN/FLG heterostructure at 77 K. The pump pulse was at \({E}_{\mathrm{pump}}=1.409\,\mathrm{eV}\) and right-circularly polarized (\({\sigma }^{+}\)). A broadband probe pulse (\({E}_{\text{probe}}=\mathrm{1.55\mbox{--}1.91}\,\text{eV}\)) with the same polarization (\({\sigma }^{+}\)) measures the pump-induced change of the heterostructure reflectance. b, A horizontal line cut at \(E=1.714\,\mathrm{eV}\) shows the optical AC Stark shift at time zero (\(\Delta t=0\)), which follows the pump pulse intensity envelope (FWHM of 230 fs). c, A pump-probe spectrum measured with a left-circularly polarized (\({\sigma }^{-}\)) probe pulse, where the optical a.c. Stark shift signal is absent. The color scale is saturated at the ±30% of the maximum level in a. d, A horizontal line cut at \(E=1.60\,\mathrm{eV}\) shows that the hot-carrier-induced broadband reflectance change of FLG appears and disappears in 370 fs (FWHM).