Antiferromagnetism versus Kondo screening in the two-dimensional periodic Anderson model at half filling: Variational cluster approach

Horiuchi, S.; Kudo, Sanae; Shirakawa, Tomonori; Ohta, Y.

doi:10.1103/physrevb.78.155128

Cited by 11 publications

(14 citation statements)

References 16 publications

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“…[42][43][44] In the case of finite doping, the self-consistent second-order perturbation approach by Mutou 45 showed that this model favors a metallic ground state, in which the quasiparticle f band is located around the Fermi level. However, this study did not take into account the c-f pairing state.…”

Section: Resultsmentioning

confidence: 99%

“…It is known that at half-filling the periodic Anderson model has an insulating ground state, [39][40][41] which exhibits antiferromagnetic order when the Coulomb repulsion is larger than the critical value U c . [42][43][44] In the case of finite doping, the self-consistent second-order perturbation approach by Mutou 45 showed that this model favors a metallic ground state, in which the quasiparticle f band is located around the Fermi level. However, this study did not take into account the c-f pairing state.…”

Section: Resultsmentioning

confidence: 99%

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Formation of Cooper pairs between conduction and localized electrons in heavy-fermion superconductors

Masuda

Yamamoto

2013

Phys. Rev. B

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Cooper pairing between a conduction electron (c electron) and an f electron, referred to as the "c-f pairing," is examined to explain s-wave superconductivity in heavy-fermion systems. We first apply the Schrieffer-Wolff transformation to the periodic Anderson model assuming deep f level and strong Coulomb repulsion. The resulting effective Hamiltonian contains direct and spin-exchange interactions between c and f electrons, which are responsible for the formation of the c-f Cooper pairs. The mean-field analysis shows that the fully gapped c-f pairing phase with anisotropic s-wave symmetry appears in a large region of the phase diagram. We also find two different types of exotic c-f pairing phases, the Fulde-Ferrell and breached pairing phases. The formation of the c-f Cooper pairs is attributed to the fact that the strong Coulomb repulsion makes a quasiparticle f band near the center of the conduction band.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Formation of Cooper pairs between conduction and localized electrons in heavy-fermion superconductors

Masuda

Yamamoto

2013

Phys. Rev. B

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“…We employ the VCA [22] to investigate a possible symmetry broken magnetic ordered state. Here, we introduce, as a variational parameter, a uniform field h on the hydrogen impurity sites [25] described as…”

Section: Variational Cluster Approximationmentioning

confidence: 99%

Emergence of massless Dirac quasiparticles in correlated hydrogenated graphene with broken sublattice symmetry

et al. 2016

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Using the variational cluster approximation (VCA) and the cluster perturbation theory, we study the finite temperature phase diagram of a half-depleted periodic Anderson model on the honeycomb lattice at half filling for a model of graphone, i.e., single-side hydrogenated graphene. The ground state of this model is found to be ferromagnetic (FM) semi-metal. The origin of this FM state is attributed to the instability of a flat band located at the Fermi energy in the noninteracting limit and is smoothly connected to the Lieb-Mattis type ferromagnetism. The spin wave dispersion in the FM state is linear in momentum at zero temperature but becomes quadratic at finite temperatures, implying that the FM state is fragile against thermal fluctuations. Indeed, our VCA calculations find that the paramagnetic (PM) state dominates the finite temperature phase diagram. More surprisingly, we find that massless Dirac quasiparticles with the linear energy dispersion emerge at the Fermi energy upon introducing the electron correlation U at the impurity sites in the PM phase. The Dirac Fermi velocity is found to be highly correlated to the quasiparticle weight of the emergent massless Dirac quasiparticles at the Fermi energy and monotonically increases with U . These unexpected massless Dirac quasiparticles are also examined with the Hubbard-I approximation and the origin is discussed in terms of the spectral weight redistribution involving a large energy scale of U . Considering an effective quasiparticle Hamiltonian which reproduces the single-particle excitations obtained by the Hubbard-I approximation, we argue that the massless Dirac quasiparticles are protected by the electron correlation. Our finding is therefore the first example of the emergence of massless Dirac quasiparticles due to dynamical electron correlations without breaking any spatial symmetry. The experimental implications of our results for graphone as well as a graphene sheet on transition metal substrates are also briefly discussed.

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“…Besides antiferromagnetism [56,61,62,63], spiral phases [64], ferromagnetism [55], d-wave superconductivity [65,66,67,68,69,70,71], charge order [72,73] and orbital order [74] have been investigated. The fact that an explicit expression for a thermodynamical potential is available allows to study discontinuous transitions and phase separation as well.…”

Section: Spontaneous Symmetry Breakingmentioning

confidence: 99%

“…The possibility to study spontaneous symmetry breaking using the VCA with suitably chosen Weiss fields as variational parameters has been exploited frequently in the past. Besides antiferromagnetism [56,61,62,63], spiral phases [64], ferromagnetism [55], d-wave superconductivity [65,66,67,68,69,70,71], charge order [72,73] and orbital order [74] have been investigated. The fact that an explicit expression for a thermodynamical potential is available allows to study discontinuous transitions and phase separation as well.…”

Section: Spontaneous Symmetry Breakingmentioning

confidence: 99%

Static and dynamic variational principles for strongly correlated electron systems

Potthoff¹

2011

AIP Conference Proceedings

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Abstract. The equilibrium state of a system consisting of a large number of strongly interacting electrons can be characterized by its density operator. This gives a direct access to the groundstate energy or, at finite temperatures, to the free energy of the system as well as to other static physical quantities. Elementary excitations of the system, on the other hand, are described within the language of Green's functions, i.e. time-or frequency-dependent dynamic quantities which give a direct access to the linear response of the system subjected to a weak time-dependent external perturbation. A typical example is angle-revolved photoemission spectroscopy which is linked to the single-electron Green's function. Since usually both, the static as well as the dynamic physical quantities, cannot be obtained exactly for lattice fermion models like the Hubbard model, one has to resort to approximations. Opposed to more ad hoc treatments, variational principles promise to provide consistent and controlled approximations. Here, the Ritz principle and a generalized version of the Ritz principle at finite temperatures for the static case on the one hand and a dynamical variational principle for the single-electron Green's function or the self-energy on the other hand are introduced, discussed in detail and compared to each other to show up conceptual similarities and differences. In particular, the construction recipe for non-perturbative dynamic approximations is taken over from the construction of static mean-field theory based on the generalized Ritz principle. Within the two different frameworks, it is shown which types of approximations are accessible, and their respective weaknesses and strengths are worked out. Static Hartree-Fock theory as well as dynamical mean-field theory are found as the prototypical approximations.

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Antiferromagnetism versus Kondo screening in the two-dimensional periodic Anderson model at half filling: Variational cluster approach

Cited by 11 publications

References 16 publications

Formation of Cooper pairs between conduction and localized electrons in heavy-fermion superconductors

Formation of Cooper pairs between conduction and localized electrons in heavy-fermion superconductors

Emergence of massless Dirac quasiparticles in correlated hydrogenated graphene with broken sublattice symmetry

Static and dynamic variational principles for strongly correlated electron systems

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