Polaron and bipolaron formation in the Hubbard-Holstein model: Role of next-nearest-neighbor electron hopping

The mechanisms for Fe(III) oxide reduction by Geobacter species are of interest because Geobacter species have been shown to play an important role in Fe(III) oxide reduction in a diversity of environments in which Fe(III) reduction is a geochemically significant process. Geobacter species specifically express pili during growth on Fe(III) oxide compared with growth on soluble chelated Fe(III), and mutants that cannot produce pili are unable to effectively reduce Fe(III) oxide. The pili of Geobacter sulfurreducens are electrically conductive along their length under physiologically relevant conditions and exhibit a metallic-like conductivity similar to that observed previously in synthetic organic metals. Metallic-like conductivity in a biological protein filament is a previously unrecognized mechanism for electron transport that differs significantly from the more well-known biological strategy of electron hopping/tunnelling between closely spaced redox-active proteins. The multihaem c-type cytochrome OmcS is specifically associated with pili and is necessary for Fe(III) oxide reduction. However, multiple lines of evidence, including the metallic-like conductivity of the pili and the fact that OmcS molecules are spaced too far apart for electron hopping/tunnelling, indicate that OmcS is not responsible for long-range electron conduction along the pili. The role of OmcS may be to facilitate electron transfer from the pili to Fe(III) oxide. Long-range electron transport via pili with metallic-like conductivity is a paradigm shift that has important implications not only for Fe(III) oxide reduction, but also for interspecies electron exchange in syntrophic microbial communities as well as microbe–electrode interactions and the emerging field of bioelectronics.

Download Full-text

CHARGE CARRIER MASS IN HIGH Tc SUPERCONDUCTORS

International Journal of Modern Physics B ◽

10.1142/s0217979299003477 ◽

1999 ◽

Vol 13 (29n31) ◽

pp. 3582-3584

Author(s):

MARCO ZOLI

Keyword(s):

Charge Carrier ◽

Numerical Study ◽

Small Polaron ◽

Electron Mass ◽

High Tc Superconductors ◽

High Tc ◽

Effective Masses ◽

Polaron Theory ◽

Holstein Model

The theory of polarons has experienced a surge of activity in the last years partly due to the possible role of polaronic quasiparticles in high Tc superconductors. This numerical study of the Holstein model shows that the polaronic effective masses become essentially dimension independent and of order ≃10–50 times the electron mass at sufficiently strong intermolecular coupling forces. Such values (which are much lower than those obtained by traditional small polaron theory) would erase one the serious objections against a (bi)polaronic picture for high Tc superconductors.

Download Full-text

The role of on-site and nearest-neighbor interactions in the correlated two-particles quantum walk

Solid State Communications ◽

10.1016/j.ssc.2016.04.027 ◽

2016 ◽

Vol 242 ◽

pp. 68-73 ◽

Cited By ~ 1

Author(s):

A.S. Peixoto ◽

W.S. Dias

Keyword(s):

Nearest Neighbor ◽

Quantum Walk

Download Full-text

ON SPATIAL CONSENSUS FORMATION: IS THE SZNAJD MODEL DIFFERENT FROM A VOTER MODEL?

International Journal of Modern Physics C ◽

10.1142/s0129183103005467 ◽

2003 ◽

Vol 14 (10) ◽

pp. 1331-1354 ◽

Cited By ~ 41

Author(s):

LAXMIDHAR BEHERA ◽

FRANK SCHWEITZER

Keyword(s):

Computer Simulations ◽

Nearest Neighbor ◽

Temporal Evolution ◽

Relaxation Times ◽

Nearest Neighbors ◽

Voter Model ◽

Consensus Formation ◽

Spatio Temporal ◽

Update Rules

In this paper, we investigate the so-called "Sznajd Model" (SM) in one dimension, which is a simple cellular automata approach to consensus formation among two opposite opinions (described by spin up or down). To elucidate the SM dynamics, we first provide results of computer simulations for the spatio-temporal evolution of the opinion distribution L(t), the evolution of magnetization m(t), the distribution of decision times P(τ) and relaxation times P(μ). In the main part of the paper, it is shown that the SM can be completely reformulated in terms of a linear voter model (VM), where the transition rates towards a given opinion are directly proportional to frequency of the respective opinion of the second-nearest neighbors (no matter what the nearest neighbors are). So, the SM dynamics can be reduced to one rule, "Just follow your second-nearest neighbor". The equivalence is demonstrated by extensive computer simulations that show the same behavior between SM and VM in terms of L(t), m(t), P(τ), P(μ), and the final attractor statistics. The reformulation of the SM in terms of a VM involves a new parameter σ, to bias between anti- and ferromagnetic decisions in the case of frustration. We show that σ plays a crucial role in explaining the phase transition observed in SM. We further explore the role of synchronous versus asynchronous update rules on the intermediate dynamics and the final attractors. As compared to the original SM, we find three additional attractors, two of them related to an asymmetric coexistence between the opposite opinions.

Download Full-text