... Basis states may be chosen for the OPSP eigenspace in analogy with sinkx and sinky; these eig... more ... Basis states may be chosen for the OPSP eigenspace in analogy with sinkx and sinky; these eigenstates are symmetric under simultaneous interchange of momentum and frequency labels (k---k+Hl,ac)n-(Aw), but are complex conju-gated ... 9. See also VL Berezinskii, Pis'ma Zh. ...
simulations are used to investigate the competition between superconducting and Peierlscharge-den... more simulations are used to investigate the competition between superconducting and Peierlscharge-density-wave (CDW) correlations in a two-dimensional electron-phonon system. The dependence of these correlations on the band filling (n), phonon frequency too, and electronphonon coupling g is examined. The Peierls-CDW correlations are favored as (n) moves towards half-filling, coo decreases, and g increases. When the Peierls-CDW correlations are weak, the Monte Carlo results for the superconducting correlations are found to be in excellent agreement with the results obtained using the well-known Eliashberg approximation.
ABSTRACT By introducing a rotationally invariant Stratonovich-Hubbard (S-H) field we studied the ... more ABSTRACT By introducing a rotationally invariant Stratonovich-Hubbard (S-H) field we studied the doped Mott insulator phase of the two-dimension Hubbard model for U/t similar to 4-8. The static spin is decoupled by the S-H field and the static charge interaction is then treated by Hartree-Fock approximation. We sample random spin configurations by Monte Carlo simulation with the Metropolis updating algorithm. The Mott-Hubbard gap and static susceptibilities are studied near the half-filling at low temperature.
We describe an iterative technique for solution of the de Dominicis-Martin parquet equations for ... more We describe an iterative technique for solution of the de Dominicis-Martin parquet equations for lattice electrons and state the relationship of this approach to conserving extensions of Hartree-Fock theory. We propose a physically motivated and computationally feasible pseudopotential approximation, which allows the solution of the parquet equations for the two-dimensional Hubbard model. We present calculations of static and dynamic Hubbard-model correlation functions based on the pseudopotential parquet and a simpler conserving approximation. For a wide parameter range the pseudopotential parquet results are in nearly quantitative agreement with finite-lattice quantum Monte Carlo results.
The phase boundary between normal and superconducting phases of the negative-U Hubbard model is o... more The phase boundary between normal and superconducting phases of the negative-U Hubbard model is obtained within a self-consistent weak-coupling approach known as the ``pseudopotential parquet'' approximation. The shortcomings of simpler self-consistent approaches, including the Hartree-Fock and fluctuation-exchange approximations, are outlined. For intermediate values of U, pseudopotential parquet predicts (i) a maximum in the superconducting transition temperature Tc at an electron filling of approximately 0.92; and (ii) a sharp decrease in Tc for values of closer to 1. The scale of transition temperatures is consistent with results from quantum simulations.
... The Cu02 Hamiltonian for holes takes the form p(Nd+—N~)= t d g — (d;,p&, +H.c.) (... more ... The Cu02 Hamiltonian for holes takes the form p(Nd+—N~)= t d g — (d;,p&, +H.c.) (il )s — pgn;, +(e — p) gn&, ... Finally, at points in our discussion we refer to results for the one-band Hubbard model pN= —t g (c— ;,c,+H.c.) — pg n;+ U g n;&n;& . I I + Ud g n;tn;), ...
When superconductivity results from the exchange of electronic excitations (spin or charge fluctu... more When superconductivity results from the exchange of electronic excitations (spin or charge fluctuations), the development of a gap is expected to modify the pairing potential below Tc. One aspect of this feedback phenomenon, pair weakening, is investigated within a modified BCS treatment of d-wave superconductivity in the Hubbard model. It is argued that pair weakening and pair breaking (inelastic scattering)
Page 1. Review of techniques in the large-N expansion for dilute magnetic alloys ... 925 926 927 ... more Page 1. Review of techniques in the large-N expansion for dilute magnetic alloys ... 925 926 927 927 930 933 937 I. OYERVl EW A. introductory remarks In this paper we review a new approach, the large-degeneracy expansion, for investigating models of dilute magnetic alloys. ...
... REVIEW LETTERS Conserving Approximations for Strongly Correlated Electron Systems: Bethe-Salp... more ... REVIEW LETTERS Conserving Approximations for Strongly Correlated Electron Systems: Bethe-Salpeter Equation and Dynamics for the Two-Dimensional Hubbard Model NE Bickers (a) Institute for Theoretical Physics, University of California at Santa Barbara, Santa Barbara ...
... Basis states may be chosen for the OPSP eigenspace in analogy with sinkx and sinky; these eig... more ... Basis states may be chosen for the OPSP eigenspace in analogy with sinkx and sinky; these eigenstates are symmetric under simultaneous interchange of momentum and frequency labels (k---k+Hl,ac)n-(Aw), but are complex conju-gated ... 9. See also VL Berezinskii, Pis'ma Zh. ...
simulations are used to investigate the competition between superconducting and Peierlscharge-den... more simulations are used to investigate the competition between superconducting and Peierlscharge-density-wave (CDW) correlations in a two-dimensional electron-phonon system. The dependence of these correlations on the band filling (n), phonon frequency too, and electronphonon coupling g is examined. The Peierls-CDW correlations are favored as (n) moves towards half-filling, coo decreases, and g increases. When the Peierls-CDW correlations are weak, the Monte Carlo results for the superconducting correlations are found to be in excellent agreement with the results obtained using the well-known Eliashberg approximation.
ABSTRACT By introducing a rotationally invariant Stratonovich-Hubbard (S-H) field we studied the ... more ABSTRACT By introducing a rotationally invariant Stratonovich-Hubbard (S-H) field we studied the doped Mott insulator phase of the two-dimension Hubbard model for U/t similar to 4-8. The static spin is decoupled by the S-H field and the static charge interaction is then treated by Hartree-Fock approximation. We sample random spin configurations by Monte Carlo simulation with the Metropolis updating algorithm. The Mott-Hubbard gap and static susceptibilities are studied near the half-filling at low temperature.
We describe an iterative technique for solution of the de Dominicis-Martin parquet equations for ... more We describe an iterative technique for solution of the de Dominicis-Martin parquet equations for lattice electrons and state the relationship of this approach to conserving extensions of Hartree-Fock theory. We propose a physically motivated and computationally feasible pseudopotential approximation, which allows the solution of the parquet equations for the two-dimensional Hubbard model. We present calculations of static and dynamic Hubbard-model correlation functions based on the pseudopotential parquet and a simpler conserving approximation. For a wide parameter range the pseudopotential parquet results are in nearly quantitative agreement with finite-lattice quantum Monte Carlo results.
The phase boundary between normal and superconducting phases of the negative-U Hubbard model is o... more The phase boundary between normal and superconducting phases of the negative-U Hubbard model is obtained within a self-consistent weak-coupling approach known as the ``pseudopotential parquet'' approximation. The shortcomings of simpler self-consistent approaches, including the Hartree-Fock and fluctuation-exchange approximations, are outlined. For intermediate values of U, pseudopotential parquet predicts (i) a maximum in the superconducting transition temperature Tc at an electron filling of approximately 0.92; and (ii) a sharp decrease in Tc for values of closer to 1. The scale of transition temperatures is consistent with results from quantum simulations.
... The Cu02 Hamiltonian for holes takes the form p(Nd+—N~)= t d g — (d;,p&, +H.c.) (... more ... The Cu02 Hamiltonian for holes takes the form p(Nd+—N~)= t d g — (d;,p&, +H.c.) (il )s — pgn;, +(e — p) gn&, ... Finally, at points in our discussion we refer to results for the one-band Hubbard model pN= —t g (c— ;,c,+H.c.) — pg n;+ U g n;&n;& . I I + Ud g n;tn;), ...
When superconductivity results from the exchange of electronic excitations (spin or charge fluctu... more When superconductivity results from the exchange of electronic excitations (spin or charge fluctuations), the development of a gap is expected to modify the pairing potential below Tc. One aspect of this feedback phenomenon, pair weakening, is investigated within a modified BCS treatment of d-wave superconductivity in the Hubbard model. It is argued that pair weakening and pair breaking (inelastic scattering)
Page 1. Review of techniques in the large-N expansion for dilute magnetic alloys ... 925 926 927 ... more Page 1. Review of techniques in the large-N expansion for dilute magnetic alloys ... 925 926 927 927 930 933 937 I. OYERVl EW A. introductory remarks In this paper we review a new approach, the large-degeneracy expansion, for investigating models of dilute magnetic alloys. ...
... REVIEW LETTERS Conserving Approximations for Strongly Correlated Electron Systems: Bethe-Salp... more ... REVIEW LETTERS Conserving Approximations for Strongly Correlated Electron Systems: Bethe-Salpeter Equation and Dynamics for the Two-Dimensional Hubbard Model NE Bickers (a) Institute for Theoretical Physics, University of California at Santa Barbara, Santa Barbara ...
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