Double-Time Green Functions in Statistical Physics

Zubarev, D. N.

doi:10.1070/pu1960v003n03abeh003275

Cited by 1,895 publications

(592 citation statements)

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“…?, 2 and 5 we calculated the equations of motion (EOM) of the Green's functions G( k, ω) and F ( k, ω), respectively corresponding to c-and d-electrons defined in Eqs. 9 and 10, using Zubarev's formalism 67 . We obtained the set of exact equations of motion detailed in Eqs.…”

Section: Discussionmentioning

confidence: 99%

“…, where the timedependent operators appear in Heisenberg representation, and the expectation value is calculated using the appropriate statistical ensemble at finite temperature T (or the ground state of the system, at T=0 ) 67 . In our case, we study the normal state of the system at temperature T , and in particular evaluate the required expectation values in the paramagnetic normal phase, using the grand canonical ensemble.…”

Section: Microscopic Model and Analytical Approachmentioning

confidence: 99%

“…We calculated the temperature-dependent Green's functions using Zubarev's equations of motion (EOM) formalism, 67,68 i.e. :…”

Section: Microscopic Model and Analytical Approachmentioning

confidence: 99%

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Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides

et al. 2016

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Using a second-order perturbative Green's functions approach we determined the normal state spectral function A( k, ω) employing a minimal model for ferropnictides. Used before to study magnetic fluctuations and superconducting properties, it includes the two effective bands related to Fe-3d orbitals proposed by S. Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and local intra-and inter-orbital correlations for the effective orbitals. Here, we focus on the normal state electronic properties, in particular the temperature and doping dependence of the total density of states, A(ω), and of A( k, ω) in different Brillouin zone regions, comparing them with existing angle resolved photoemission spectroscopy (ARPES) and theoretical results. We obtain an asymmetric effect of electron and hole doping, quantitative agreement with the experimental chemical potential shifts, as well as spectral weight redistributions near the Fermi level with temperature consistent with the available experiments. In addition, we predict a non-trivial dependence of A(ω) with temperature, exhibiting clear renormalization effects by correlations. Interestingly, investigating the origin of this predicted behaviour by analyzing the evolution with temperature of the k-dependent self-energy obtained in our approach, we could identify a number of Brillouin zone points, not probed by ARPES yet, where the largest non-trivial effects of temperature on the renormalization are predicted for the parent compounds.

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Section: Discussionmentioning

confidence: 99%

Section: Microscopic Model and Analytical Approachmentioning

confidence: 99%

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Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides

et al. 2016

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“…where | H denotes the Zubarev notation [17], and where the subscriptH indicates that a given correlator is governed by the transformed Hamiltonian (12). In particular, the equation of motion for the function…”

Section: Model and Methodsmentioning

confidence: 99%

Phonon-assisted Andreev reflection in a hybrid junction based on a quantum dot

Bocian

Rudziński

2015

Eur. Phys. J. B

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Abstract. Spin-dependent tunneling through a quantum dot coupled to one ferromagnetic and one superconducting electrodes is investigated in the Andreev reflection (AR) regime occurring in the presence of the on-dot electron-phonon interactions. Current-voltage characteristics of the system are evaluated within the nonequilibrium Green function technique. Features of the AR current due to interplay between the electron-phonon interactions, intradot Coulomb correlations and the polarization of the ferromagnetic electrode are analyzed in both linear and nonlinear transport regimes. It is shown that for the case of electron-hole symmetry, the phonon resonances may appear on both sides of the main elastic resonances in spectral function. A phonon-induced renormalization of the Andreev transmission levels is found and splitting of the phonon side bands for nonvanishing intradot Coulomb repulsion is observed. It is shown that linear conductance exhibits the polaron shift and suppression in the presence of the polaron transmission. In nonequilibrium situation the mechanism of the negative differential conductance (NDC) in the presence of competing magnetic electrode polarisation and the Coulomb correlations on the dot is analyzed. An influence of the polaron transmission through the Andreev intradot states on the NDC oscillations is also discussed.

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“…To get the equation of motion we use the double-time temperature dependent retarded Green function is given by (Zubarev) [24]:…”

Section: Pairing Of Superconducting and Ferromagnetic Order Paramentioning

confidence: 99%

Coexistence of Superconductivity and Ferromagnetism in Intermetallic Uranium-Based Superconductors UCoGe, UIr and UGe2

Brhane¹

2014

IOSRJEN

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-Starting with a model Hamiltonian for the system with equal spin singlet and triplet pairings based on quantum field theory and green function formalism, we obtain expressions for superconductivity and ferromagnetism parameters. The model exhibits a distinct possibility of the coexistence of superconductivity and ferromagnetism, which are two usually irreconcilable cooperative phenomena, however, recently ferromagnetism and superconductivity have been shown to coexist simultaneously in the newly discovered compounds such as UCoGe, UIr and UGe 2 .The work is motivated by the recent experimental evidences below the superconducting phase temperature in a number of uranium-based superconductors. The theoretical results are then applied to show the coexistence of superconductivity and ferromagnetism in the intermetallic uraniumbased compound UCoGe, UIr and UGe 2 . The limitations of the model are also discussed.

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Double-Time Green Functions in Statistical Physics

Cited by 1,895 publications

References 2 publications

Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides

Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides

Phonon-assisted Andreev reflection in a hybrid junction based on a quantum dot

Coexistence of Superconductivity and Ferromagnetism in Intermetallic Uranium-Based Superconductors UCoGe, UIr and UGe2

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