摘要：SummaryUtilizing high-pressure to modulate optical properties, such as thermoreflectance (dR/dT), over a wide range has received much attention. Nevertheless, how the pressure exerts on the complex dielectric constant and finally ondR/dTremains elusive. Here, we perform a thoroughly experimental and theoretical investigation ondR/dTof Al nano-film from 0 to 25 GPa. ThedR/dTvalues exhibit a sine-like pressure-dependence, with the zero-crossing appearing at around 6 GPa. These special phenomena are well explained from electron transition viewpoints. Thefirst-principlescalculations show that the energy difference of parallel bands is enlarged from 1.45 to 2 eV, thereby increasing the threshold for electron transitions. The lifted threshold changes the optical absorption rates of Al and the density of states of the electrons involving interband transitions; finally, the resultingdR/dTexhibits such a pressure-dependent behavior. Our findings provide a deep insight on pressure-induced electronic transitions and photon-electron interactions in metals.Graphical abstractDisplay OmittedHighlights•Thermoreflectance (dR/dT) of Al films was measured under a pressure range of 0–25 GPa•A semi-quantum model well describes the pressure effect on optical properties•Pressure enlarges interband transition energy which makesdR/dTpressure-dependent•The resonant interband transitions letdR/dTchange to negative at ∼6 GPaCondensed matter physics; Nanotechnology; Materials synthesis
