14 March 2023 Tue 4 pm

We present the results of a dynamical study of 1-MeV positrons channeling in a short chiral single-wall carbon nanotube (11, 9). The positron-nanotube interaction potential was constructed using longitudinally averaged positron-carbon interaction potential. In the classical treatment, we analyze the spatial channeling functions and the corresponding distributions of channeled positrons at various channeling depths. We also identify the caustic lines of the trajectory family and the corresponding rainbows maxima appearing distributions of channeled particles. In the quantum treatment of the problem, the corresponding one-dimensional time-dependent Schrödinger equation was solved for the incident positron initially represented by a wide Gaussian wave packet. The distribution of singularities of the quantum phase function (i.e., places where positrons probability density is equal to zero) and its influence on the quantum potential was investigated. The Bohm positron trajectories and their finite-time Lyapunov exponents were analyzed as well. We have found that the proliferation of the phase singularities causes the positive limiting value of the finite-time Lyapunov characteristic exponent. This signals that Bohmian positron dynamics is neither regular nor chaotic but complex.

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