You are cordially invited to the seminar of the Scientific Computing Laboratory of the Center for the Study of Complex Systems and of the project Polaron Mobility in Model Systems and Real Materials (PolMoReMa). The seminar will be held on Thursday, 6 November 2025 at 14:00 in the "Zvonko Marić" lecture hall of the Institute of Physics Belgrade. The talk entitled

Quantum dynamics of charge transport in the field of slow off-diagonal dynamic disorder

will be given by Dr Veljko Janković (Scientific Computing Laboratory, Institute of Physics Belgrade). The abstract of the talk:

The motion of a charge carrier in organic molecular crystals is mainly limited by its moderate coupling to slow and abundantly thermally excited intermolecular phonons [1]. Despite recent advances in fully quantum methods, computations of transport properties most often rely on Newtonian [2] or some effective phonon dynamics [3]. This holds true even for the one-dimensional Peierls model featuring a single phonon mode per lattice site [4].

In this second SCL & PolMoReMa seminar, we present our numerically exact hierarchical equations of motion (HEOM)-based framework to compute transport properties of the one-dimensional Peierls model [5,6]. The phonon-assisted current is handled using our explicit expression of HEOM auxiliary operators in terms of phonon creation and annihilation operators [5]. We find that the displaced Drude peak [3] is accompanied by an optical-conductivity enhancement below phonon frequency [6], which is not observed in experimental low-frequency signatures. Solving the dissipaton equations of motion for a more realistic model with a continuous distribution of phonon modes, we conclude that this enhancement is an artifact of the assumed delta-like density of phonon states [7].

This research is supported by the Science Fund of the Republic of Serbia, Grant No. 5468, Polaron Mobility in Model Systems and Real Materials – PolMoReMa.

[1] B. M. T. C. Peluso et al., Angew. Chem. Int. Ed. 2025, e202507566 (2025).
[2] A. Troisi and G. Orlandi, Phys. Rev. Lett. 96, 086601 (2006).
[3] S. Fratini, D. Mayou, and S. Ciuchi, Adv. Funct. Mater. 26, 2292 (2016).
[4] J. E. Runeson, T. J. G. Drayton, and D. E. Manolopoulos, J. Chem. Phys. 161, 144102 (2024).
[5] V. Janković, Phys. Rev. B 112, 035111 (2025).
[6] V. Janković, Phys. Rev. B 112, 035112 (2025).
[7] V. Janković, arXiv:2508.14447 (2025).