Breakdown of Polarons in Conducting Polymers at Device Field Strengths

Abstract

Conducting polymers have become standard engineering materials, used in many electronic devices. Despite this, there is a lack of understanding of the microscopic origin of the conducting properties, especially at realistic device field strengths. We present simulations of doped poly(p-phenylene) (PPP) using a Su-Schrieffer-Heeger (SSH) tight-binding model, with the electric field included in the Hamiltonian through a time-dependent vector potential via Peierls substitution of the phase factor. We find that polarons typically break down within less than a picosecond after the field has been switched on, already for electric fields as low as around 1.6 mV/Å. This is a field strength common in many flexible organic electronic devices. Our results challenge the relevance of the polaron as charge carrier in conducting polymers for a wide range of applications.

Bipolarons in a Bose-Einstein Condensate

“…Bipolarons stand out as an important example of the opposite limit, where two quasiparticles, socalled polarons, form a bound state much smaller than the average distance between the unbound polarons. The formation of bipolarons is suggested to be the mechanism behind electrical conduction in polymer chains [5,6], organic magnetoresistance [7], and even high temperature superconductivity [8,9].…”

Pattern formation in one-dimensional polaron systems and temporal orthogonality catastrophe

“…In material science polarons are encountered in several classes of technologically relevant materials, for instance, in He droplets [2,3], polar [4][5][6][7][8] or organic [9][10][11] semiconductors and transition metal oxides [12,13], while their broad relevance stretches even towards biophysics [14]. Their formation, properties and interactions are key elements in important phenomena such as the electric conductivity of polymers [15,16], the organic magnetoresistance [17], the Kondo effect [18] and even high-temperature superconductivity [19][20][21][22][23][24]. Therefore, it is not surprising that ultracold atoms, being one of the prime platforms for quantum simulation [25], have been employed for studying polaronic structures.…”

Dynamical formation of polarons in a Bose-Einstein condensate: A variational approach

“…When an electron travels through a material, it gets dressed by the low-energy excitations of the lattice (phonons), forming a polaron with renormalised energy and mass [2]. Polarons give insight into transport properties in semiconductors [3], electrical conduction in polymer chains [4], spin transport in organic materials [5,6] and superconductivity [7]. Moreover, they can be used as a "probe" for highly correlated quantum many-body environments as well, for instance, 3 He impurities immersed into 4 He superfluids [8].…”

“…Polarons give insight into transport properties in semiconductors [3], electrical conduction in polymer chains [4], spin transport in organic materials [5,6] and superconductivity [7]. Moreover, they can be used as a "probe" for highly correlated quantum many-body environments as well, for instance, 3 He impurities immersed into 4 He superfluids [8].…”