Metallic state in disordered quasi-one-dimensional conductors

Abstract

The unusual metallic state in conjugated polymers and single-walled carbon nanotubes is studied by dielectric spectroscopy (8-600 GHz). We have found an intriguing correlation between scattering time and plasma frequency. This relation excludes percolation models of the metallic state. Instead, the carrier dynamics can be understood in terms of the low density of delocalized states around the Fermi level, which arises from the competion between disorder-induced localization and interchaininteractions-induced delocalization.The finite conductivity of a metal at zero Kelvin is a consequence of the lattice-periodicity and the finite density of states at the Fermi level (E F ). By breaking translational symmetry, disorder localizes chargecarriers. Upon growing disorder, eventually a metalinsulator transition (MIT) occurs [1], the effect being the stronger the lower the dimensionality. In one dimension (1D) any disorder localizes the electronic states. The MIT in quasi-1D conducting polymers and single-walled carbon nanotubes is also disorder-driven, but its exact nature is under severe debate. Many authors claim the presence of a "heterogeneous" state in which the relevant disorder length-scale is large compared to the electronic correlation-length. In this case, the MIT corresponds to a percolation transition of metallic islands embedded in an amorphous matrix. [2][3][4] Other studies suggest that the MIT is of the Anderson type [1] with disorder occurring on length-scales equal or less than the electronic correlation-length. [5,6] Then, extended and localized states are separated in energy by the mobility edge (E c ), and the MIT occurs when E F crosses E c .

6 GHz microstrip patch antennas with PEDOT and polypyrrole conducting polymers

“…CPs also exhibit dispersion in their electrical conductivity with frequency [8][9][10]. Therefore, the measured results differed from the simulated results not only due to fabrication errors, but also due to dispersion in electrical conductivity.…”

Order–disorder transitions in poly(3,4-ethylenedioxythiophene)

“…Conductivity mechanisms in oxidized (doped) conjugated polymers such as poly(acetylene) [10,11], poly(aniline) [11,12], poly(pyrrole) and PEDT [12,13] are commonly reported as being limited by hopping or tunnelling with conductivity data being well fitted by Drude theory. It was assumed that this hopping existed between ordered 'metallic' domains [14].…”

Thermally Induced Transient Absorption of Light by Poly(3,4‐ethylenedioxythiophene):Poly(styrene sulfonic acid) (PEDOT:PSS) Films: A Way to Probe Charge‐Carrier Thermalization Processes

“…Values reported for doped conducting polymers range from 5 ps to a few femtoseconds. [11] Previously, we have reported on transient changes in the resistance of PEDOT:PSS induced by infrared light. [12] This effect has been used to construct a polymer infrared detector with a detectivity D* close to 10 5 cm (Ö Hz) W ±1 at 1.18 eV.…”