Quantum Switching of π‑Electron
Rotations
in a Nonplanar Chiral Molecule by Using Linearly Polarized UV Laser
Pulses
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Abstract
Nonplanar chiral aromatic molecules are candidates for
use as building
blocks of multidimensional switching devices because the π electrons
can generate ring currents with a variety of directions. We employed
(<i>P</i>)-2,2′-biphenol because four patterns of
π-electron rotations along the two phenol rings are possible
and theoretically determine how quantum switching of the π-electron
rotations can be realized. We found that each rotational pattern can
be driven by a coherent excitation of two electronic states under
two conditions: one is the symmetry of the electronic states and the
other is their relative phase. On the basis of the results of quantum
dynamics simulations, we propose a quantum control method for sequential
switching among the four rotational patterns that can be performed
by using ultrashort overlapped pump and dump pulses with properly
selected relative phases and photon polarization directions. The results
serve as a theoretical basis for the design of confined ultrafast
switching of ring currents of nonplanar molecules and further current-induced
magnetic fluxes of more sophisticated systems