Strong variation of dielectric response and optical properties of lithium under pressure

Strong modification of bonding and electronic properties in lithium under pressure becomes the origin of its striking departure from the classical nearly-free-electron-like model. In this Brief Report, we predict the existence of a low-energy long-lived interband electronic collective mode arising with the bcc to fcc structural transition in lithium under pressure, which is expected to induce an abrupt plasma edge in the experimentally observable reflectivity and also affect electronic correlations at low energies.