Lessons on electronic decoherence in molecules from exact modeling

Abstract

Electronic decoherence processes in molecules and materials are usually thought and modeled via schemes for the system-bath evolution in which the bath is treated either implicitly or approximately. Here we present computations of the electronic decoherence dynamics of a model many-body molecular system described by the Su-Schrieffer-Heeger Hamiltonian with Hubbard electron-electron interactions using an exact method in which both electronic and nuclear degrees of freedom are taken into account explicitly and fully quantum mechanically. To represent the electron-nuclear Hamiltonian in matrix form and propagate the dynamics, the computations employ the Jordan-Wigner transformation for the fermionic creation/annihilation operators and the discrete variable representation for the nuclear operators. The simulations offer a standard for electronic decoherence that can be used to test approximations. They also provide a useful platform to answer fundamental questions about electronic decoherence that cannot be addressed through approximate or implicit schemes. Specifically, through simulations, we isolate basic mechanisms for electronic coherence loss and demonstrate that electronic decoherence is possible even for one-dimensional nuclear bath. Furthermore, we show that (i) decreasing the mass of the bath generally leads to faster electronic decoherence; (ii) electron-electron interactions strongly affect the electronic decoherence when the electron-nuclear dynamics is not pure-dephasing; (iii) classical bath models with initial conditions sampled from the Wigner distribution accurately capture the short-time electronic decoherence dynamics; (iv) model separable initial superpositions often used to understand decoherence after photoexcitation are only relevant in experiments that employ delta-like laser pulses to initiate the dynamics. These insights can be employed to interpret and properly model coherence phenomena in molecules.

Manipulating nonadiabatic conical intersection dynamics by optical cavities

“…However, the environment for the molecular motion (e.g., solvent) may have a large inuence on the nonadiabatic polaritonic dynamics through ultrafast electronic decoherence processes. [39][40][41] We introduce an external environment…”

When can quantum decoherence be mimicked by classical noise?

“…Even when this condition is not strictly satisfied, the pure-dephasing effects may still be the dominant effect when the environment dynamics is non-resonant with the transition frequencies of the system such that the dissipation is much slower compared to pure-dephasing effects. For this reason, the pure-dephasing limit has been useful in describing electronic decoherence in molecules [4,6], elastic electron-phonon interaction in solid state systems, loss of quantum interference [19], line shape in spectroscopic measurements [20], vibrational dephasing in solvents [29] and the central spin problem [18].…”

“…The inevitable interaction between a quantum system with its surrounding environment leads to decoherence [1][2][3][4][5][6]. The decoherence occurs because such interaction leads to systembath entanglement that turns a pure system state to a statistical mixture of states.…”

Electronic interactions do not affect electronic decoherence in the pure-dephasing limit

“…[3][4][5][6][7][8][9][10] The nuclei act as an environment that induces a loss of phase relationship between the electronic states. Understanding the mechanisms for electronic decoherence is of vital importance for understanding the ground-and excited-state dynamics of molecules, 5,6,8,9 for developing accurate approximations to model correlated electron-nuclear dynamics 11,12 and for preserving electronic coherence that can subsequently be used to enhance molecular functions. 13 A fundamental question that arises in this context is what is the mutual influence of electron-electron interactions and electronic decoherence.…”

“…14 More precisely, whether decoherence can induce changes in the electronic correlation and, conversely, whether electron-electron interactions can modify the electronic decoherence dynamics. In a recent exact numerical study of electronic decoherence for the Su-Schrieffer-Heeger (SSH) Hamiltonian amended by the Hubbard electronrepulsion term, 6 it was shown that while the electron-electron interactions can induce a significant change of the electronic decoherence by introducing and modifying avoided crossings among the Potential Energy Surfaces (PESs), they do not a) ignacio.franco@rochester.edu influence the decoherence when the dynamics is puredephasing in nature. That is, when the nuclei do not introduce significant transitions among electronic diabatic states.…”