1,840 research outputs found

### From d- to p-wave pairing in the t-t' Hubbard model at zero temperature

We develop a DCA(PQMC) algorithm which employs the projective quantum Monte
Carlo (PQMC) method for solving the equations of the dynamical cluster
approximation (DCA) at zero temperature, and apply it for studying pair
susceptibilities of the two-dimensional Hubbard-model with next-nearest
neighbor hopping. In particular, we identify which pairing symmetry is dominant
in the U-n parameter space (U: repulsive Coulomb interaction; n: electron
density). We find that p_{x+y}- (d_{x^2-y^2}-) wave is dominant among triplet
(singlet) pairings -at least for 0.3<n<0.8 and U<=4t. The crossover between
d_{x^2-y^2}-wave and p_{x+y}-wave occurs around n~0.4.Comment: 5 pages 5 figures; two additional panels in Fig. 2; as to appear in
Phys. Rev.

### Electronic Structure of Sodium Cobalt Oxide: Comparing Mono- and Bilayer-hydrate

To shed new light on the mechanism of superconductivity in sodium cobalt
oxide bilayer-hydrate (BLH), we perform a density functional calculation with
full structure optimization for BLH and its related nonsuperconducting phase,
monolayer hydrate (MLH). We find that these hydrates have similar band
structures, but a notable difference can be seen in the $a_{1g}$ band around
the Fermi level. While its dispersion in the $z$ direction is negligibly small
for BLH, it is of the order of 0.1 eV for MLH. This result implies that the
three dimensional feature of the $a_{1g}$ band may be the origin for the
absence of superconductivity in MLH.Comment: 5 pages, 7 figures, to be published in Phys. Rev.

### Matrix product solution to an inhomogeneous multi-species TASEP

We study a multi-species exclusion process with inhomogeneous hopping rates.
This model is equivalent to a Markov chain on the symmetric group that
corresponds to a random walk in the affine braid arrangement. We find a matrix
product representation for the stationary state of this model. We also show
that it is equivalent to a graphical construction proposed by Ayyer and
Linusson, which generalizes Ferrari and Martin's construction

### Correlation effects on magnetic frustration in the triangular-lattice Hubbard model

Evolution of the magnetic response function in the triangular-lattice Hubbard
model is studied with interaction strength within a systematic
inverse-degeneracy expansion scheme which incorporates self-energy and vertex
corrections and explicitly preserves the spin-rotation symmetry. It is shown
that at half filling the response function goes through a nearly dispersionless
regime around K for intermediate coupling strength, before undergoing an
inversion at strong coupling, resulting in maximum response at the K point,
consistent with the expected 120^o AF instability. Effects of finite
hole/electron doping on the magnetic response function are also examined.Comment: 20 pages, 9 figure

### Remarks on the multi-species exclusion process with reflective boundaries

We investigate one of the simplest multi-species generalizations of the one
dimensional exclusion process with reflective boundaries. The Markov matrix
governing the dynamics of the system splits into blocks (sectors) specified by
the number of particles of each kind. We find matrices connecting the blocks in
a matrix product form. The procedure (generalized matrix ansatz) to verify that
a matrix intertwines blocks of the Markov matrix was introduced in the periodic
boundary condition, which starts with a local relation [Arita et al, J. Phys. A
44, 335004 (2011)]. The solution to this relation for the reflective boundary
condition is much simpler than that for the periodic boundary condition

### Mechanism of charge transfer/disproportionation in LnCu3Fe4O12 (Ln: Lanthanides)

The Fe-Cu intersite charge transfer and Fe charge disproportionation are
interesting phenomena observed in some LnCu3Fe4O12 (Ln: Lanthanides) compounds
containing light and heavy Ln atoms, respectively. We show that a change in the
spin state is responsible for the intersite charge transfer in the light Ln
compounds. At the high spin state, such systems prefer an unusual Cu-d^8
configuration, whereas at the low spin state they retreat to the normal Cu-d^9
configuration through a charge transfer from Fe to Cu-3d_{xy} orbital. We find
that the strength of the crystal field splitting and the relative energy
ordering between Cu-3d_{xy} and Fe-3d states are the key parameters,
determining the intersite charge transfer (charge disproportionation) in light
(heavy) Ln compounds. It is further proposed that the size of Ln affects the
onsite interaction strength of Cu-3d states, leading to a strong modification
of the Cu-L_3 edge spectrum, as observed by the X-ray absorption spectroscopy.Comment: 6 pages, 5 figures, 1 table. To appear in PR

### Orbital-selective Mott-Hubbard transition in the two-band Hubbard model

Recent advances in the field of quantum Monte Carlo simulations for impurity
problems allow --within dynamical mean field theory-- for a more thorough
investigation of the two-band Hubbard model with narrow/wide band and
SU(2)-symmetric Hund's exchange. The nature of this transition has been
controversial, and we establish that an orbital-selective Mott-Hubbard
transition exists. Thereby, the wide band still shows metallic behavior after
the narrow band became insulating -not a pseudogap as for an Ising Hund's
exchange. The coexistence of two solutions with metallic wide band and
insulating or metallic narrow band indicates, in general, first-order
transitions.Comment: 4 pages, 3 figures; 2nd version as published in Phys. Rev. B (R);
minor corrections, putting more emphasis on differences in spectra when
comparing SU(2) and Ising Hund's exchang

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