Femtosecond dynamics of correlated many-body states in C$_{60}$ fullerenes

TL;DR

This study investigates the ultrafast electronic and vibrational dynamics in C60 fullerenes using two-photon photoionization and theoretical modeling, revealing femtosecond-scale electronic relaxation and vibrational energy dissipation.

Contribution

It provides new insights into the femtosecond-scale correlated many-body electronic and vibrational dynamics in C60, combining experimental measurements with ab initio theoretical analysis.

Findings

Electronic relaxation time lower limit: ~10 fs

Vibrational energy dissipation time: ~400 fs

Theoretical explanation via nonadiabatic vibronic couplings

Abstract

Fullerene complexes may play a key role in the design of future molecular electronics and nanostructured devices with potential applications in light harvesting using organic solar cells. Charge and energy flow in these systems is mediated by many-body effects. We studied the structure and dynamics of laser-induced multi-electron excitations in isolated C$_{60}$ by two-photon photoionization as a function of excitation wavelength using a tunable fs UV laser and developed a corresponding theoretical framework on the basis of \emph{ab initio} calculations. The measured resonance line width gives direct information on the excited state lifetime. From the spectral deconvolution we derive a lower limit for purely electronic relaxation on the order of $\tau_\mathrm{el}=10^{+5}_{-3}$ fs. Energy dissipation towards nuclear degrees of freedom is studied in time-resolved techniques. The evaluation of the non-linear autocorrelation trace gives a characteristic time constant of $\tau_\mathrm{vib}=400\pm100$ fs for the exponential decay. In line with the experiment, the observed transient dynamics is explained theoretically by nonadiabatic (vibronic) couplings involving the correlated electronic, the nuclear degrees of freedom (accounting for the Herzberg-Teller coupling), and their interplay.