Spontaneous Charge Carrier Localization in Extended One-Dimensional Systems

Abstract

Charge carrier localization in extended atomic systems has been described previously as being driven by disorder, point defects or distortions of the ionic lattice. Here we show for the first time by means of first-principles computations that charge carriers can spontaneously localize due to a purely electronic effect in otherwise perfectly ordered structures. Optimally-tuned range-separated density functional theory and many-body perturbation calculations within the GW approximation reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange-induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies and the optimally-tuned range parameter itself all become independent of polymer length as it exceeds the critical localization scale. Moreover, lattice disorder and the formation of a polaron result from the charge localization in contrast to the traditional view that lattice distortions precede charge localization. Our results can explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses.

Swift GW beyond 10,000 electrons using sparse stochastic compression

“…The resulting stochastic GW method reproduces the results of deterministic GW [20] but is very fast so it is applicable to large systems with thousands of valance electrons. [19,21,22] Here, two major improvements of stochastic GW are introduced, and together they enable routine calculations of QP energies for systems with N e > 10, 000. The first relates to the projection of random functions to the occupied subspace.…”

Stochastic Formulation of the Resolution of Identity: Application to Second Order Møller–Plesset Perturbation Theory

“…We note, for example, that in certain situations the Full Configuration-Interaction Quantum Monte Carlo approach can handle systems with tens of electrons [9][10][11][12] Likewise, Auxiliary-Field Monte which replaces the two-body interaction by an interaction with fluctuating densities and the fixednode approximation [28] when combined with the Shifted-Contour approach [29] give excellent results for systems with tens of electrons. [30] For large systems containing hundreds or thousands of electrons several of the authors have developed stochastic methods for DFT and TDDFT [21,26,27,31], MP2 [19,24], GF2 [32], GW [25,[33][34][35] and the Bethe-Salpeter equation [25].…”

Universal Exciton Size in Organic Polymers is Determined by Nonlocal Orbital Exchange in Time-Dependent Density Functional Theory

“…This aspect is of high importance in the discussion of localization effects in finite π-systems, a topic that is intensely debated. [9][10][11][12][13] While previous work was focused on a qualitative rationalization of excitonic effects, [14][15][16][17] a quantitative perspective is adopted here which allows to decompose excitonic effects in large conjugated π-systems on different levels. Furthermore, a hierarchy of exchange-correlation (xc) functionals is investigated in terms of their ability to describe excitonic properties, i.e.…”