Asymmetry induces long-lasting energy current transients inside molecular loop circuits

Energy transport and conversion at nanoscale have become an important topic of fundamental and applied research, in particular for conceiving ground-breaking solutions in energy-aware digital electronics and energy production. In this work, we propose a formal framework to address time-dependent energy transport inside quantum networks. The approach permits us to investigate how energy transferred to electrons by a femtosecond laser pulse is stored and released in a molecular circuit consisting of two donor-acceptor branches connected to an acceptor chain. Additionally, the two donors may be coupled, creating a loop inside the circuit. Time-resolved analysis reveals that when a difference exists between the two donor-acceptor branches, a loop current occurs and persists during relaxation, while only a small amount of current flows through the acceptor chain. A long-lasting energy flow thus emerges from the asymmetry of the molecular structure.