A new functional integral formalism for the degenerate Anderson model

Read, N.; Newns, D. M.

doi:10.1088/0022-3719/16/29/007

Cited by 196 publications

(121 citation statements)

References 9 publications

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“…Approximation schemes for calculating G f,b which violate the gauge symmetry would, hence, violate the orthogonality of initial and final states, and should be expected to give incorrect results for physical quantities, even though certain aspects of the Fermi liquid fixed point can be described by symmetry-breaking approximations 32,33,34,35,36,37,38 . Therefore, we take great care to preserve the gauge symmetry.…”

Section: Model and Conserving T-matrix Approximationmentioning

confidence: 99%

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

2004

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The Anderson model of a twofold spin degenerate impurity level in the limit of infinite Coulomb repulsion, U → ∞, coupled to one and two degenerate conduction bands or channels, is considered in pseudo-particle representation. We extend the Conserving T-Matrix Approximation (CTMA), a general diagrammatic approximation scheme based on a fully renormalized computation of twoparticle vertex functions in the spin and in the charge channel, to the calculation of thermodynamic and spectral properties. In the single-channel case, the CTMA yields in the Kondo regime a temperature independent Pauli spin susceptibility for temperatures below the Kondo temperature TK and down to the lowest temperatures considered, reproducing the exact spin screening in the Fermi liquid state. The impurity spectral density appears to remain non-singular down to the lowest temperatures, in agreement with Fermi liquid behavior. However, the unitarity sum rule, which is crucial for an impurity solver like the CTMA to be applicable within Dynamical Mean Field Theories for strongly correlated lattice models, is overestimated at the lowest temperatures. We argue that this shortcoming may be due to numerical imprecision and discuss an appropriate scheme for its correction. In the two-channel case, the spectral density calculated within CTMA exhibits qualitatively the correct non-Fermi liquid behavior at low temperatures, i.e. a powerlaw singularity.

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Section: Model and Conserving T-matrix Approximationmentioning

confidence: 99%

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

2004

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“…It underlies the theoretical model we will use in the paper. The system of interacting f holes and conduction band holes can be described using the lattice Anderson Hamiltonian in the slave boson representation: [30,34,35] …”

Section: Modelmentioning

confidence: 99%

Theory of first-order isostructural valence phase transitions in the mixed valence compoundsYbIn1−xAgx
Goltsev
¹
,
Bruls
²

2001
Phys. Rev. B
26
1
17
0
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For describing the first-order isostructural valence phase transition in mixed valence compounds we develop a new approach based on the lattice Anderson model. We take into account the Coulomb interaction between localized f and conduction band electrons and two mechanisms of electronlattice coupling. One is related to the volume dependence of the hybridization. The other is related to local deformations produced by f shell size fluctuations accompanying valence fluctuations. The large f -state degeneracy allows us to use the 1/N expansion method. Within the model we develop a mean-field theory for the first-order valence phase transition in YbInCu4. It is shown that the Coulomb interaction enhances the exchange interaction between f and conduction band electron spins and is the driving force of the phase transition. A comparison between the theoretical calculations and experimental measurements of the valence change, susceptibility, specific heat, entropy, elastic constants and volume change in YbInCu4 and YbAgCu4 are presented, and a good quantitative agreement is found. On the basis of the model we describe the evolution from the first-order valence phase transition to the continuous transition into the heavy-fermion ground state in the series of compounds YbIn1−xAgxCu4. The effect of pressure on physical properties of YbInCu4 is studied and the H − T phase diagram is found. 71.27+a,75.20.Hr

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“…Large N theories are well known in particle physics 11 and in heavy fermion theory 12,13,14 , but they were first introduced in quantum magnetism by Berlin and Kac, who solved the spherical model of ferromagnetism exactly in a large N limit 15 . Simultaneously, Anderson, Dyson and Maleev introduced spin wave theory, which takes the spin S to be large and expands in 1/S 16,17,18 .…”

Section: Introductionmentioning

confidence: 99%

SymplecticNand time reversal in frustrated magnetism

Flint

Coleman

2009

Phys. Rev. B

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Identifying the time reversal symmetry of spins as a symplectic symmetry, we develop a large N approximation for quantum magnetism that embraces both antiferromagnetism and ferromagnetism. In SU (N ), N > 2, not all spins invert under time reversal, so we have introduced a new large N treatment which builds interactions exclusively out of the symplectic subgroup[SP (N )] of time reversing spins, a more stringent condition than the symplectic symmetry of previous SP (N ) large N treatments. As a result, we obtain a mean field theory that incorporates the energy cost of frustrated bonds. When applied to the frustrated square lattice, the ferromagnetic bonds restore the frustration dependence of the critical spin in the Néel phase, and recover the correct frustration dependence of the finite temperature Ising transition.

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A new functional integral formalism for the degenerate Anderson model

Cited by 196 publications

References 9 publications

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

Theory of first-order isostructural valence phase transitions in the mixed valence compoundsYbIn1−xAgx
Goltsev
¹
,
Bruls
²

2001
Phys. Rev. B
26
1
17
0
View full text Add to dashboard Cite

SymplecticNand time reversal in frustrated magnetism

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A new functional integral formalism for the degenerate Anderson model

Cited by 196 publications

References 9 publications

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

Dynamical properties of the Anderson impurity model within a diagrammatic pseudoparticle approach

Theory of first-order isostructural valence phase transitions in the mixed valence compoundsYbIn1−xAgxGoltsev1, Bruls2 2001Phys. Rev. B261170View full textAdd to dashboardCite

SymplecticNand time reversal in frustrated magnetism

Contact Info

Product

Resources

About

Theory of first-order isostructural valence phase transitions in the mixed valence compoundsYbIn1−xAgx
Goltsev
¹
,
Bruls
²

2001
Phys. Rev. B
26
1
17
0
View full text Add to dashboard Cite