scholarly journals Quantum and thermal fluctuations in a two-dimensional correlated band ferromagnet: Goldstone-mode-preserving investigation with self-energy and vertex corrections

2007 ◽  
Vol 76 (10) ◽  
Author(s):  
Sudhakar Pandey ◽  
Avinash Singh
Keyword(s):  
Thermal Fluctuations ◽  
Goldstone Mode ◽  
Two Dimensional ◽  
Self Energy ◽  
Vertex Corrections

scholarly journals Vertex Corrections in Gauge Theories for Two-dimensional Condensed Matter Systems

1998 ◽  
Vol 12 (16n17) ◽  
pp. 1673-1692 ◽  
Author(s):  
Peter Kopietz
Keyword(s):  
Gauge Field ◽  
Condensed Matter ◽  
Finite Energy ◽  
Energy Scale ◽  
Gauge Fields ◽  
Logarithmic Correction ◽  
Two Dimensional ◽  
Numerical Constant ◽  
Self Energy ◽  
Vertex Corrections

We calculate the self-energy of two-dimensional fermions that are coupled to transverse gauge fields, taking two-loop corrections into account. Given a bare gauge field propagator that diverges for small momentum transfers q as 1/qη, 1<η≤ 2, the fermionic self-energy without vertex corrections vanishes for small frequencies ω as Σ(ω)∝ ωγ with γ=2/(1+η)<1. We show that inclusion of the leading radiative correction to the fermion-gauge field vertex leads to Σ(ω)∝ωγ [1-aη ln (ω0/ω)], where aη is a positive numerical constant and ω0 is some finite energy scale. The negative logarithmic correction is consistent with the scenario that higher order vertex corrections push the exponent γ to larger values.

Mobility of spin polarons with vertex corrections

2019 ◽  
Vol 33 (18) ◽  
pp. 1950195
Author(s):  
Marcielow J. Callelero ◽  
Danilo M. Yanga
Keyword(s):  
Order Term ◽  
Hard Core ◽  
Hole Mobility ◽  
Boltzmann Distribution ◽  
Temperature Limit ◽  
Self Energy ◽  
Vertex Corrections ◽  
Bosonic Operator ◽  
Dirac Distribution ◽  
Ising Limit

The mobility of holes in the spin polaron theory is discussed in this paper using a representation where holes are described as spinless fermions and spins as normal bosons. The hard-core bosonic operator is introduced through the Holstein–Primakoff transformation. Mathematically, the theory is implemented in the finite temperature (Matsubara) Green’s function method. The expressions for the zeroth-order term of the hole mobility is determined explicitly for hole occupation factor taking the form of Fermi–Dirac distribution and the classical Maxwell–Boltzmann distribution function. These are proportional to the relaxation time and the square of the renormalization factor. In the Ising limit, we showed that the mobility is zero and the holes are localized. The calculation of the hole mobility is generalized by considering the vertex corrections, which included the ladder diagrams. One of the vertex functions in the hole mobility can be evaluated using the Ward identity for hole-spin wave weak interaction. We also derived an expression for the hole mobility with vertex corrections in the low-temperature limit and vanishing self-energy effects. Our calculation is made up to second-order correction in the case where the hole occupation factor follows the Fermi–Dirac distribution.

scholarly journals DUFFIN–KEMMER–PETIAU THEORY IN THE CAUSAL APPROACH

2002 ◽  
Vol 17 (02) ◽  
pp. 205-227 ◽  
Author(s):  
J. T. LUNARDI ◽  
B. M. PIMENTEL ◽  
J. S. VALVERDE ◽  
L. A. MANZONI
Keyword(s):  
Compton Scattering ◽  
Gauge Invariance ◽  
Vacuum Polarization ◽  
Effective Theory ◽  
Self Energy ◽  
Vertex Corrections ◽  
Causal Approach ◽  
Scalar Sector ◽  
Natural Way

In this paper we consider the scalar sector of Duffin–Kemmer–Petiau theory in the framework of Epstein–Glaser causal method. We calculate the lowest order distributions for Compton scattering, vacuum polarization, self-energy and vertex corrections. By requiring gauge invariance of the theory we recover, in a natural way, the scalar propagator of the usual effective theory.

Superfluidity of the Lattice Anyon Gas

1989 ◽  
Vol 03 (12) ◽  
pp. 1965-1995 ◽  
Author(s):  
Eduardo Fradkin
Keyword(s):  
Quantum Hall ◽  
Goldstone Mode ◽  
Two Dimensional ◽  
Hall Conductance ◽  
Dimensional Lattice ◽  
Quantum Hall Systems ◽  
Wigner Transformation ◽  
Topological Invariance ◽  
Quantum Hall System ◽  
Chern Simons

I consider a gas of “free” anyons with statistical paremeter δ on a two dimensional lattice. Using a recently derived Jordan-Wigner transformation, I map this problem onto a gas of fermions on a lattice coupled to a Chern-Simons gauge theory with coupling [Formula: see text]. I show that if [Formula: see text] and the density [Formula: see text], with r and q integers, the system is a superfluid. If q is even and the system is half filled the state may be either a superfluid or a Quantum Hall System depending on the dynamics. Similar conclusions apply for other values of ρ and δ. The dynamical stability of the Fetter-Hanna-Laughlin goldstone mode is insured by the topological invariance of the quantized Hall conductance of the fermion problem. This leads to the conclusion that anyon gases are generally superfluids or quantum Hall systems.

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