1,003 research outputs found
Extremely Correlated Fermi Liquid Description of Normal State ARPES in Cuprates
The normal state single particle spectral function of the high temperature
superconducting cuprates, measured by the angle resolved photoelectron
spectroscopy (ARPES), has been considered both anomalous and crucial to
understand. Here we show that an unprecedentedly detailed description of the
data is provided by a spectral function arising from the Extremely Correlated
Fermi Liquid state of the t-J model proposed recently by Shastry. The
description encompasses both laser and conventional synchrotron ARPES data on
optimally doped BiSrCaCuO, and also conventional
synchrotron ARPES data on the LaSrCuO materials. {\em It
fits all data sets with the same physical parameter values}, satisfies the
particle sum rule and successfully addresses two widely discussed "kink"
anomalies in the dispersion.Comment: Published version, 5 figs; published 29 July (2011
Hubbard Model on Decorated Lattices
We introduce a family of lattices for which the Hubbard model and its natural
extensions can be quasi-exactly solved, i.e. solved for the ground and low
energy states. In particular, we show rigorously that the ground state of the
Hubbard model with off-site Coulomb repulsions on a decorated Kagom\`{e}
lattice is an ordered array of local currents. The low energy theory describing
this chiral state is an XY model, where each spin degree of freedom
represents the two possible chiralities of each local current.Comment: Accepted in Phys. Rev. Let
Universal features of Thermopower in High Tc systems and Quantum Criticality
In high Tc superconductors a wide ranging connection between the doping
dependence of the transition temperature Tc and the room temperature
thermopower Q has been observed. A "universal correlation" between these two
quantities exists with the thermopower vanishing at optimum doping as noted by
OCTHH (Obertelli, Cooper, Tallon, Honma and Hor). In this work we provide an
interpretation of this OCTHH universality in terms of a possible underlying
quantum critical point (QCP) at Tc. Central to our viewpoint is the recently
noted Kelvin formula relating the thermopower to the density derivative of the
entropy. Perspective on this formula is gained through a model calculation of
the various Kubo formulas in an exactly solved 1-dimensional model with various
limiting procedures of wave vector and frequency.Comment: 12 pages, 8 figure
Solution of Some Integrable One-Dimensional Quantum Systems
In this paper, we investigate a family of one-dimensional multi-component
quantum many-body systems. The interaction is an exchange interaction based on
the familiar family of integrable systems which includes the inverse square
potential. We show these systems to be integrable, and exploit this
integrability to completely determine the spectrum including degeneracy, and
thus the thermodynamics. The periodic inverse square case is worked out
explicitly. Next, we show that in the limit of strong interaction the "spin"
degrees of freedom decouple. Taking this limit for our example, we obtain a
complete solution to a lattice system introduced recently by Shastry, and
Haldane; our solution reproduces the numerical results. Finally, we emphasize
the simple explanation for the high multiplicities found in this model
Microscopic mechanism for the 1/8 magnetization plateau in SrCu_2(BO_3)_2
The frustrated quantum magnet SrCu_2(BO_3)_2 shows a remarkably rich phase
diagram in an external magnetic field including a sequence of magnetization
plateaux. The by far experimentally most studied and most prominent
magnetization plateau is the 1/8 plateau. Theoretically, one expects that this
material is well described by the Shastry-Sutherland model. But recent
microscopic calculations indicate that the 1/8 plateau is energetically not
favored. Here we report on a very simple microscopic mechanism which naturally
leads to a 1/8 plateau for realistic values of the magnetic exchange constants.
We show that the 1/8 plateau with a diamond unit cell benefits most compared to
other plateau structures from quantum fluctuations which to a large part are
induced by Dzyaloshinskii-Moriya interactions. Physically, such couplings
result in kinetic terms in an effective hardcore boson description leading to a
renormalization of the energy of the different plateaux structures which we
treat in this work on the mean-field level. The stability of the resulting
plateaux are discussed. Furthermore, our results indicate a series of stripe
structures above 1/8 and a stable magnetization plateau at 1/6. Most
qualitative aspects of our microscopic theory agree well with a recently
formulated phenomenological theory for the experimental data of SrCu_2(BO_3)_2.
Interestingly, our calculations point to a rather large ratio of the magnetic
couplings in the Shastry-Sutherland model such that non-perturbative effects
become essential for the understanding of the frustrated quantum magnet
SrCu_2(BO_3)_2.Comment: 24 pages, 24 figure
Resonant Two-Magnon Raman Scattering and Photoexcited States in Two-Dimensional Mott Insulators
We investigate the resonant two-magnon Raman scattering in two-dimensional
(2D) Mott insulators by using a half-filled 2D Hubbard model in the strong
coupling limit. By performing numerical diagonalization calculations for small
clusters, we find that the Raman intensity is enhanced when the incoming photon
energy is not near the optical absorption edge but well above it, being
consistent with experimental data. The absence of resonance near the gap edge
is associated with the presence of background spins, while photoexcited states
for resonance are found to be characterized by the charge degree of freedom.
The resonance mechanism is different from those proposed previously.Comment: REVTeX4, 4 pages, 3 figures, to be published in Phys. Rev. Let
Exact solution and spectral flow for twisted Haldane-Shastry model
The exact solution of the spin chain model with exchange is found for
twisted boundary conditions. The spectrum thus obtained can be reproduced by
the asymptotic Bethe ansatz. The spectral flow of each eigenstate is determined
exactly as a function of the twist angle. We find that the period for
the ground state nicely fits in with the notion of fractional exclusion
statistics.Comment: 4 pages, revtex, 1 figure available on request, to appear in PR
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