Ivanov Anatoly I
Volgograd State University, University Avenue 100, Volgograd 400062, Russia.
J Chem Phys. 2025 Jan 14;162(2). doi: 10.1063/5.0243375.
The first excited state of conjugated donor-acceptor molecules of C3 symmetry (octupolar molecules) is doubly degenerate. Such a doublet is known to be isomorphic to a spin 1/2. It is shown that a large electric dipole moment is associated with this spin. Since the mean value of the electric dipole moment of an octupolar molecule is a measure of the symmetry breaking charge transfer, a dimensionless dipole moment called the dissymmetry vector is introduced. The dissymmetry vector operator is constructed. A linear tensor connection between this operator and the Pauli matrices is found. The tensor character is due to the two-dimensionality of the dipole moment. The dipole moment can rotate freely in the plane of the molecule as long as the C3 symmetry is maintained. The rotation is associated only with the rearrangement of the electronic subsystem of the molecule and does not affect the spatial position of the nuclei. This opens up the possibility of changing the dipole moment state on a subpicosecond time scale. The Jahn-Teller effect on the dissymmetry vector is considered in detail. It is shown that the dissymmetry vector can be controlled using electric fields in the same way as three-dimensional spin if both static and alternating electric fields are in the plane of the molecule. The conducted studies indicate that the dipole moment of excited octupolar molecules is a promising candidate for the physical implementation of a qubit.
具有C3对称性的共轭供体-受体分子（八极分子）的第一激发态是双重简并的。已知这样的二重态与自旋1/2同构。结果表明，这个自旋与一个大的电偶极矩相关。由于八极分子电偶极矩的平均值是对称性破缺电荷转移的一种度量，因此引入了一个无量纲的偶极矩，称为不对称向量。构建了不对称向量算符。发现了该算符与泡利矩阵之间的线性张量联系。张量特性源于偶极矩的二维性。只要保持C3对称性，偶极矩就能在分子平面内自由旋转。这种旋转仅与分子电子子系统的重新排列有关，而不影响原子核的空间位置。这就开辟了在亚皮秒时间尺度上改变偶极矩状态的可能性。详细考虑了 Jahn-Teller 效应 对不对称向量的影响。结果表明，如果静态电场和交变电场都在分子平面内，那么可以像控制三维自旋一样，利用电场来控制不对称向量。所进行的研究表明，激发态八极分子的偶极矩是量子比特物理实现的一个有前途的候选者。
