Probing spin-charge relation by magnetoconductance in one-dimensional polymer nanofibers

Abstract

Polymer nanofibers are one-dimensional organic hydrocarbon systems containing conducting polymers where the nonlinear local excitations such as solitons, polarons, and bipolarons formed by the electronphonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here, we report our observations of a qualitatively differentMC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA, the MC is essentially zero, but it is present in PANI and PT. The universal scaling behavior and the zero (finite)MC in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge). Polymer nanofibers are one-dimensional organic hydrocarbon systems containing conducting polymers where the nonlinear local excitations such as solitons, polarons, and bipolarons formed by the electron-phonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here, we report our observations of a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA, the MC is essentially zero, but it is present in PANI and PT. The universal scaling behavior and the zero (finite) MC in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge). Disciplines Physical Sciences and Mathematics | Physics

Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers

“…Nonetheless, refinements in chemical synthesis of polymers have contributed to greater reproducibility of experimental data on transport across experiments. For instance, a variety of polymer nanofibers including polyacetylene (PA), polypyrrole (PPy), polyaniline (PANI), and polythiophene (PT) have been shown to display power law dependence of conductance in temperature, G ( T ) ∝  T α and current-voltage characteristic, I ( V ) ∝  V β in a wide range of T and V parameters67. Electrical transport through polymer nanofibers including such power law dependence can be explained, within some limited range of T and V , in the framework of variable range hopping (VRH)8, fluctuation induced tunneling (FIT)9, electric field induced tunneling101112, manifestation of Luttinger liquid (LL) and environmental Coulomb blockade (ECB)67.…”

“…where I 0 , α , β , γ are the fitting parameters, k B is the Boltzmann constant, e is the electron charge, and Γ( x ) is the gamma function6713141516. The expression for macroscopic current described by Eq.…”

“…The functional form of Eq. 1 has been observed to describe variety of 1D or quasi-1D systems6720212223. Remarkably, the scaling has also been observed beyond 1D systems in conducting polymer films such as poly(2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene) (PBTTT)131415 and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)1416, and theories such as polaron hopping in semiconducting polymers15, ECB16, and VRH242526 have been developed to explain these findings.…”

Quasi one dimensional transport in individual electrospun composite nanofibers

“…7 The characteristic fingerprint for quasi-one dimensional behavior is a power-law dependence of the conductance with temperature and of the current with applied potential. The power-law was observed in various systems ranging from carbon nanotubes, 1-3, 6-8 conducting conjugated polymer nanowires, 5,[9][10][11] semiconductors nanowires 4,12,13 and fractional quantum Hall edge states. 14 One way of obtaining continuous nanofibers is by electrospinning.…”

“…Electron-electron interactions are a main player in one dimensional transport bringing about behavior different from the classic Fermi liquid. Different kinds of behaviors are associated with electron-electron interactions: Luttinger liquid behavior resulting from repulsive short range electron-electron interactions, [1][2][3][4][5] Wigner crystal behavior resulting from long range Coulomb interaction 6 or environmental Coulomb blockade. 7 The characteristic fingerprint for quasi-one dimensional behavior is a power-law dependence of the conductance with temperature and of the current with applied potential.…”