Normal state properties of the attractive Hubbard model: moment approach

Schneider, T.; Pedersen, M. H.; Rodríguez-Núñez, J. J.

doi:10.1007/s002570050120

Cited by 19 publications

(21 citation statements)

References 4 publications

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“…22,29,33,35,36,41,42 ). The bandwidth correction was identified to be of minor importance with respect to spontaneous magnetism, because the last two correlation functions F −σ are effectively spin independent.…”

Section: Spectral Density Approachmentioning

confidence: 99%

“…The main advantages of this method are the physically simple concept and the explicit non-perturbative character. Recent applications use the SDA successfully for the investigation of the attractive Hubbard model (U < 0) 33 , the t-J-model 34 and for studying systems with reduced dimension 29 , surface magnetism 35 and magnetism of thin films 36 . The SDA is believed to be a good starting point for the investigation of high temperature superconductivity 23,37 .…”

Section: Spectral Density Approachmentioning

confidence: 99%

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Magnetism in the single-band Hubbard model

Herrmann

Nolting

1997

Journal of Magnetism and Magnetic Materials

128

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A self-consistent spectral density approach (SDA) is applied to the Hubbard model to investigate the possibility of spontaneous ferro-and antiferromagnetism. Starting point is a two-pole ansatz for the single-electron spectral density, the free parameter of which can be interpreted as energies and spectral weights of respective quasiparticle excitations. They are determined by fitting exactly calculated spectral moments. The resulting self-energy consists of a local and a non-local part. The higher correlation functions entering the spin-dependent local part can be expressed as functionals of the single-electron spectral density. Under certain conditions for the decisive model parameters (Coulomb interaction U , Bloch-bandwidth W , band occupation n, temperature T ) the local part of the self-energy gives rise to a spin-dependent band shift, thus allowing for spontaneous band magnetism. As a function of temperature, second order phase transitions are found away from half filling, but close to half filling the system exhibits a tendency towards first order transitions. The non-local self-energy part is determined by use of proper two-particle spectral densities. Its main influence concerns a (possibly spin-dependent) narrowing of the quasiparticle bands with the tendency to stabilize magnetic solutions. The non-local self-energy part disappears in the limit of infinite dimensions. We present a full evaluation of the Hubbard model in terms of quasiparticle densities of states, quasiparticle dispersions, magnetic phase diagram, critical temperatures (TC , TN ) as well as spin and particle correlation functions. Special attention is focused on the non-locality of the electronic self-energy, for which some rigorous limiting cases are worked out.

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Section: Spectral Density Approachmentioning

confidence: 99%

Section: Spectral Density Approachmentioning

confidence: 99%

Magnetism in the single-band Hubbard model

Herrmann

Nolting

1997

Journal of Magnetism and Magnetic Materials

128

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“…We have fixed µ from the requirement given in Eq. (14). In order to fix the factor η which is introduced in Eq.…”

Section: Resultsmentioning

confidence: 99%

“…SDA is a reliable approximation in the strong coupling limit so long as the one-electron spectral density has predominantly a two-peak structure. In the literature SDA has been successfully used for the investigation of both the attractive 14 In the present work, we attempt an approximate solution of the KLM using the SDA. The aim of the present investigation is to study the conditions under which the interband exchange and band filling together cause a collective (ferromagnetic) ordering and half-metallicity of the local-moment system.…”

Section: Introductionmentioning

confidence: 99%

On the Possibility of Ferromagnetism and Half-Metallicity in Local Moment Systems

2011

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We use the Kondo lattice model to investigate the possibility of ferromagnetism and halfmetallicity in local moment systems. Using the spectral density approach and making use of the fact that the spontaneous magnetization of local moment and the itinerant electron polarization are coupled, we derive an expression for the paramagnetic susceptibility. The magnetic ordering temperature is determined from the singularities of the susceptibility. The magnetic phase diagram is constructed in T − n(band filling) plane. It is found that ferromagnetism is possible only for small values of n. It is also found that the temperature drives the transition of the system from half-metal to metal.

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“…19 These features of the spectra can be compared with numerical and approximate calculations of the oneparticle spectrum. [30][31][32][33][34][35] In Fig. 3 we show the numerical spectrum for a ten-site one-dimensional ring.…”

Section: ͑312͒mentioning

confidence: 99%

Spectral properties of the large-negative-U Hubbard model

Eskes

Oles-acute

1997

Phys. Rev. B

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Using the formalism introduced by Harris and Lange ͓Phys. Rev. 157, 295 ͑1967͔͒ explicit expressions for partial sum rules of the individual Hubbard bands in the large-negative-U limit are derived. The one-particle spectrum, optical spectrum, as well as charge-and spin-response functions are considered. The approach gives a transparent description of the main features of these spectra. The main sum rules depend on only two independent nearest-neighbor expectation values which are estimated in the ground state using numerical calculations, exact results, and linear-spin-wave theory. Simple expressions for the intensities of the upper and lower Hubbard bands in the optical conductivity show that this spectrum is extremely sensitive on details of the ground state. The charge-density wave and superconducting phases are clearly distinguishable and even the transition to the broken-symmetry state may have a detectable influence on the conductivity.

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Normal state properties of the attractive Hubbard model: moment approach

Cited by 19 publications

References 4 publications

Magnetism in the single-band Hubbard model

Magnetism in the single-band Hubbard model

On the Possibility of Ferromagnetism and Half-Metallicity in Local Moment Systems

Spectral properties of the large-negative-U Hubbard model

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