Following the Dirac-Frenkel time-dependent variational principle, dynamics of a one-dimensional Holstein polaron is probed by employing the Davydov D 2 ansatz with two sets of variational parameters, one for each constituting particle in the exciton-phonon system, and a simplified variant of the Davydov D 1 ansatz, also known as the D ansatz, with an additional set of phonon displacement parameters. A close examination of variational outputs from the two trial states reveals fine details of the polaron structure and intricacies of dynamic exciton-phonon interactions. Superradiance coherence sizes, speeds of exciton-induced phonon wave packets, linear optical absorption, and polaron energy compositions are also included in the study.

Validity of three time-dependent trial states of the Holstein Hamiltonian, namely the D(2), Merrifield and D Ansätze has been examined in detail with regards to their deviations from the exact solution to the time-dependent Schrödinger equation. Linear absorption spectra are also calculated as an additional indicator of the Ansatz validity. It is found that the D Ansatz is the most accurate trial state of the three, and all Ansätze fail to provide an adequate description of system dynamics in the weak-coupling regime.

No abstract

No abstract

For photocatalytic solar energy conversion, the critical challenge is to enhance the solar utilization efficiency. Many efforts have focused on the development of broad-band response nanomaterials. Here, we propose an alternative approach wherein, over Ni 2 P/ TiO 2 nanoparticles without noble metal, the UV−vis part of solar energy was absorbed and converted by a semiconductor and its infrared part was separately collected and converted into thermal energy to heat the photocatalytic reaction to a certain temperature. The photothermocatalytic hydrogen activity was 3.6 times that of the sum of the photocatalytic and thermocatalytic reactions. The in situ generated oxygen vacancies in Ni 2 P/TiO 2 during the photothermocatalytic reaction were found to be responsible for the enhanced activity. Moreover, the photocurrent transient response results revealed the faster transfer of electrons from TiO 2 to Ni 2 P at higher temperature which is vital for the significantly enhanced photothermocatalytic hydrogen production. The long-term test also shows the stability of the proposed reaction system.