Doublon bottleneck in the ultrafast relaxation dynamics of hot electrons in 1T-TaS_{2}

Abstract

Employing time-resolved photoelectron spectroscopy we analyze the relaxation dynamics of hot electrons in the charge density wave/Mott material 1T-TaS_{2}. At 1.2 eV above the Fermi level we observe a hot electron lifetime of 12±5 fs in the metallic state and of 60±10 fs in the broken symmetry ground state—a direct consequence of the reduced phase space for electron-electron scattering determined by the Mott gap. Boltzmann equation calculations which account for the interaction of hot electrons in a Bloch band with a doublon-holon excitation in the Mott state provide insight into the unoccupied electronic structure in the correlated state.