Programme

O.13 -- Oral, VCTP-49

Date: Friday, 2 August 2024

Time: 14:40 - 15:05

Photo-dressed state approach for generating unidirectional $\pi$-electron rotation in aromatic ring molecule

Quang Huy Ho (1), Ngoc Loan Phan (1), Gap-Sue Kim (2), Yuichi Fujimura (3), and Hirobumi Mineo (4, 5)

(1) Computational Physics Laboratory K002, Department of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City, Viet Nam; (2) Dharma College, Dongguk University, 30, Pildong-ro 1-gil, Jung-gu, Seoul, 04620, Korea; (3) Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Japan; (4) Atomic Molecular and Optical Physics Research Group, Science and Technology Advanced Institute, Van Lang University, Ho Chi Minh City, Viet Nam; (5) Faculty of Applied Technology, School of Technology, Van Lang University, Ho Chi Minh City, Viet Nam

The laser driven $\pi$-electron rotation in aromatic ring molecules is one of the typical topics of photo-controlled charged migration, which has contributed to a development of the next-generation organic electronics devices. Recently much attentions have been concentrated on the generation of unidirectional rotation of $\pi$-electron, which is induced by a strong electric field. The rapidity of unidirectional rotation has been estimated by the orbital angular momentum of $\pi$-electron using quantum chemical calculations. The unidirectional angular momentum has been investigated by irradiating the high-symmetry aromatic molecule with the UV circularly polarized laser pulse (CP laser) to instantly populate from the ground state to the pair of degenerate electronic states, which forms the angular momentum state [1]. Although low-symmetry group do not contain the pair of degenerate states, the mechanism of dressed states has been introduced utilizing the pair of equal frequency continuous linearly polarized lasers to generate the stationary angular momentum [2]. Here, the pair of linearly polarized lasers with distinct polarization directions is combined to form an elliptically polarized laser (EP laser). However, treatment of $\pi$-electron rotation of dressed states in the aromatic ring molecules has not been discussed in a fully satisfactory way in preceding works. In our research, the dressed state approach has been used to solve the time-dependent Schr\"odinger equation in the aromatic molecule with any fold symmetry (high and low symmetry) in CP or EP laser (more generally, helical laser) in quasi-quantum mechanics. In the three electronic states model, including ground and pair of degenerate excited states in case of high symmetry or pair of quasi-degenerate excited states in case of low symmetry, three dressed states have been generated, each can generate angular momentum, in which the signal of each angular momentum is associated with the corresponding dressed state. One of three angular momentums represents a ‘counter-intuitive’ of $\pi$-electron rotation in the aromatic ring, indicating that the electron’s direction rotation is opposing the direction rotation of electronic field, this cannot be explained using classical mechanics and has been considered as quantum behavior. The angular momenta of the rest two dressed states, the direction of $\pi$-electron rotation is same as that of the electronic field, which can be understood using classical mechanics, therefore two dressed states indicate the ‘intuitive’ rotation of $\pi$-electron. [1] I. Barth, J. Manz, Y. Shigeta and K. Yagi, "Unidirectional Electronic Ring Current Driven by a Few Cycle Circularly Polarized Laser Pulse: Quantum Model Simulations for Mg-Porphyrin," J. Am. Chem. Soc, vol. 128, no. 21, pp. 7043-7049, 2006. [2] M. Yamaki, Y. Teranishi, H. Nakamura, S. H. Lina and Y. Fujimura, " The generation of stationary $\pi$-electron rotations in chiral aromatic ring molecules possessing non-degenerate excited states," Phys. Chem. Chem. Phys, vol. 18, no. 3, pp. 1570-1577, 2016.

Presenter: Hồ Quang Huy