Marc G. Zacher

SYSTEMATIC NUMERICAL STUDY OF SPIN-CHARGE SEPARATION IN ONE DIMENSION

The problem of spin-charge separation is analyzed numerically in the metallic phase of the one-band Hubbard model in one dimension by studying the behavior of the single-particle Greens function and of the spin and charge susceptibilities. We first analyze the Quantum-Monte Carlo data for the imaginary-time Greens function within the Maximum Entropy method in order to obtain the spectral function at real frequencies. For some values of the momentum sufficiently away from the Fermi surface two separate peaks are found, which can be identified as charge and spin excitations. In order to improve our accuracy and to be able to extend our study to a larger portion of the Brillouin zone, we also fit our data with the imaginary-time Greens function obtained from the Luttinger-model solution with two different velocities as fitting parameters. The excitation energies associated with these velocities turn out to agree, in a broad range of momenta, with the ones calculated from the charge and spin susceptibilities. This allows us to identify these single-particle excitations as due to a separation of spin and charge. Remarkably, the range of momenta where spin-charge separation is seen extends well beyond the region of linear dispersion about the Fermi surface. We finally discuss a possible extension of our method to detect spin-charge separation numerically in two dimensions.

Evolution of the stripe phase as a function of doping from a theoretical analysis of angle-resolved photoemission data

By comparing single-particle spectral functions of

Interrelation of superconducting and antiferromagnetic gaps in high- T(c) compounds: A test case for the SO(5) theory

t\ensuremath{-}J

Where do holes go in doped antiferromagnets and what is their relationship to superconductivity

and Hubbard models with recent angle-resolved photoemission results for

STRIPES IN DOPED ANTIFERROMAGNETS: BOND-CENTERED VERSUS SITE-CENTERED

{\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}

The Cluster-Perturbation-Theory and its Application to Strongly-Correlated Materials

(LSCO) and Nd-LSCO, we can decide where holes go as a function of doping, and more specifically, which type of stripe (bond-, site-centered) is present in these materials at a given doping. For dopings greater than about

Self-Organized Quasi-One Dimensional Structures in High-Temperature Superconductors: the Stripe Phase

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Projected SO(5)-theory and the interrelation of superconducting and antiferromagnetic gaps in high-Tc compounds

our calculation shows that the holes prefer to proliferate out of the metallic stripes into the neighboring antiferromagnetic domains. The spectra were calculated by a cluster-perturbation technique, for which we present an alternative formulation. Implications for the theory for

SO(5) symmetry in t-J and hubbard models

\mathrm{high}\ensuremath{-}{T}_{c}

SO(5) theory of high-Tc superconductivity: models and experiments

superconductivity are discussed.