CHARGE-DENSITY-WAVES IN THE PRESENCE OF IMPURITY POTENTIAL IN ONE-DIMENSIONAL SYSTEMS: A FIELD THEORY APPROACH

2004 ◽  
Vol 18 (06) ◽  
pp. 883-898 ◽  
Author(s):  
L. V. BELVEDERE ◽  
R. L. P. G. DO AMARAL ◽  
A. F. DE QUEIROZ
Keyword(s):  
Charge Density ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Charge Density Waves ◽  
Lagrangian Model ◽  
Theory Approach ◽  
Density Waves ◽  
Impurity Potential ◽  
One Dimensional ◽  
Phonon Field

The effective Lagrangian model for charge-density waves interacting with an impurity potential in one-dimensional systems is considered in the dynamical phonon phase approach. Using the fermion–boson mapping we obtain the effective bosonized version of the model. The impurity potential breaks the linked electron–phonon symmetry, the phason field turns out to be in interaction with the electron–phonon condensate and the phonon field develops a non-vanishing vacuum expectation value. The effective fermionized version of the model corresponds to the chiral Gross–Neveu model with quartic self-interaction among a massless and a massive (electron) Fermi fields. The electron–phonon system exhibits a conserved topological charge which is independent of local variations of the phases of the phonon and electron fields. The equation of state of the associated statistical-mechanical system is obtained. For the dynamical phonon phase field the Kosterlitz–Thouless phase transition is suppressed.

THE FERMION-BOSON MAPPING APPLIED TO LAGRANGIAN MODELS FOR CHARGE-DENSITY-WAVES IN ONE-DIMENSIONAL SYSTEMS

2002 ◽  
Vol 16 (31) ◽  
pp. 4685-4716 ◽  
Author(s):  
L. V. BELVEDERE ◽  
R. L. P. G. AMARAL ◽  
A. F. DE QUEIROZ
Keyword(s):  
Charge Density ◽  
Chiral Symmetry ◽  
Quantum Dynamics ◽  
Charge Density Waves ◽  
Goldstone Mode ◽  
Density Waves ◽  
Effective Electron ◽  
One Dimensional ◽  
Phonon Field ◽  
Electron Field

We use the two-dimensional Fermion-Boson mapping to perform a field theory analysis of the effective Lagrangian model for incommensurate charge-density waves (ICDW) in one-dimensional systems. We consider an approach in which both the phase of the complex phonon field and the electron field are dynamical degrees of freedom contributing to the quantum dynamics and symmetry-related features of the ICDW phenomenon. We obtain the bosonized and fermionized versions of the effective electron–phonon Lagrangian. The phase of the phonon field and the phase of the bosonized chiral density of the electron field condense as a soliton order parameter, carrying neither the charge nor the chirality of the electron–phonon system, leading to a periodic sine-Gordon potential. The phonon field is fermionized in terms of a chiral fermionic condensate and the effective model is mapped into the chiral Gross–Neveu (GN) model with two Fermi field species. The linked electron–phonon symmetry of the ICDW system is mapped into the chiral symmetry of the GN model. Within the functional integral formulation, we obtain for the vacuum expectation value of the phonon field < ϕ > = 0 and < ϕ ϕ* > ≠ 0, due to the charge selection rule associated with the chiral electron–phonon symmetry. We show that the two-point correlation function of the phonon field satisfies the cluster decomposition property, as required by the chiral symmetry of the underlying GN model. The quantum description of the ICDW corresponds to charge transport through the lattice, due to the propagation of a "Goldstone mode" carrying the effective charge of the electron–phonon system, is accomplished by an electron–lattice energy redistribution. This accounts for a dynamical Peierls's energy gap generation.

Theory of pseudogaps in charge density waves in application to photo electron spectroscopy

2002 ◽  
Vol 12 (9) ◽  
pp. 73-73
Author(s):  
S. I. Matveenko ◽  
S. Brazovskii
Keyword(s):  
Charge Density ◽  
Adiabatic Approximation ◽  
Free Particle ◽  
Charge Density Waves ◽  
Photon Absorption ◽  
Electronic Excitations ◽  
Dimensional Electron ◽  
Density Waves ◽  
One Dimensional ◽  
Exponential Decrease

For a one-dimensional electron-phonon system we consider the photon absorption involving electronic excitations within the pseudogap energy range. Within the adiabatic approximation for the electron - phonon interactions these processes are described by ronlinear configurations of an instanton type. We calculate the subgap absorption as it can be observed by means of photo electron or tunneling spectroscopies. In details we consider systems with gapless modes: 1D semiconductors with acoustic phonons and incommensurate charge density waves. We found that below the free particle edge the pseudogap starts with the exponential decrease of transition rates changing to a power law deeply within the pseudogap, near the absolute edge.

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