1,407 research outputs found
Nonuniversal spectral properties of the Luttinger model
The one electron spectral functions for the Luttinger model are discussed for
large but finite systems. The methods presented allow a simple interpretation
of the results. For finite range interactions interesting nonunivesal spectral
features emerge for momenta which differ from the Fermi points by the order of
the inverse interaction range or more. For a simplified model with interactions
only within the branches of right and left moving electrons analytical
expressions for the spectral function are presented which allows to perform the
thermodynamic limit. As in the general spinless model and the model including
spin for which we present mainly numerical results the spectral functions do
not approach the noninteracting limit for large momenta. The implication of our
results for recent high resolution photoemission measurements on quasi
one-dimensional conductors are discussed.Comment: 19 pages, Revtex 2.0, 5 ps-figures, to be mailed on reques
Variational Study of the Spin-Gap Phase of the One-Dimensional t-J Model
We propose a correlated spin-singlet-pairs wave function to describe the
spin-gap phase of the one-dimensional model at low density. Adding a
Jastrow factor with a variational parameter, , first introduced by
Hellberg and Mele, is shown to correctly describe the long-range behavior
expected for the Luther-Emery phase. Using the variational Monte Carlo method
we establish a relation between and the Luttinger exponent ,
.Comment: 4 pages (LaTex), 3 figures attache
Antiferromagnetic Heisenberg chains with bond alternation and quenched disorder
We consider S=1/2 antiferromagnetic Heisenberg chains with alternating bonds
and quenched disorder, which represents a theoretical model of the compound
CuCl_{2x}Br_{2(1-x)}(\gamma-{pic})_2. Using a numerical implementation of the
strong disorder renormalization group method we study the low-energy properties
of the system as a function of the concentration, x, and the type of
correlations in the disorder. For perfect correlation of disorder the system is
in the random dimer (Griffiths) phase having a concentration dependent
dynamical exponent. For weak or vanishing disorder correlations the system is
in the random singlet phase, in which the dynamical exponent is formally
infinity. We discuss consequences of our results for the experimentally
measured low-temperature susceptibility of
CuCl_{2x}Br_{2(1-x)}(\gamma-{pic})_2
Spin-density wave versus superconducting fluctuations for quasi-one-dimensional electrons in two chains of Tomonaga-Luttinger liquids
We study possible states at low temperatures by applying the
renormalization-group method to two chains of Tomonaga-Luttinger liquids with
both repulsive intrachain interactions and interchain hopping. As the energy
decreases below the hopping energy, three distinct regions I, III, and II
appear successively depending on properties of fluctuations. The crossover from
the spin-density wave (SDW) state to superconducting (SC) state takes place in
region III where there are the excitation gaps of transverse charge and spin
fluctuations. The competition between SDW and SC states in region III is
crucial to understanding the phase diagram in the quasi-one-dimensional organic
conductors.Comment: 11 pages, Revtex format, 1 figure, to be published in Phys. Rev.
DC Josephson Effect in a Tomonaga-Luttinger Liquid
The dc Josephson effect in a one-dimensional Tomonaga-Luttinger (TL) liquid
is studied on the basis of two bosonized models. We first consider a TL liquid
sandwiched between two superconductors with a strong barrier at each interface.
Both the interfaces are assumed to be perfect if the barrier potential is
absent. We next consider a TL liquid with open boundaries, weakly coupled with
two superconductors. Without putting strong barriers, we instead assume that
the coupling at each interface is described by a tunnel junction. We calculate
the Josephson current in each model, and find that the two models yield same
results. The Josephson current is suppressed by repulsive electron-electron
interactions. It is shown that the suppression is characterized by only the
correlation exponent for the charge degrees of freedom. This result is
inconsistent with a previously reported result, where the spin degrees of
freedom also affects the suppression. The reason of this inconsistency is
discussed.Comment: 18 page
Spin Defects in Spin-Peierls Systems
We examine spin-Peierls systems in the presence of spin defects which are
introduced by replacing magnetic ions with non-magnetic ones
in . By using the action for the bosonized Hamiltonian, it
is shown directly that the antiferromagnetic state induced by the spin defects
coexists with the spin-Peierls states. Further the doping dependences of both
transition temperature of spin-Peierls state and the spin gap have been
calculated. The transition temperature of the present estimation shows good
agreement quantitatively with that observed in Cu_{1-\de} Zn_\de O_3 for the
region of the doping rate, \de<0.02.Comment: jpsj style, 11 pages, 2 figure
Economic Analysis of Carryover Policies for the United States Wheat Industry
The Oklahoma Agricultural Experiment Station periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311
Tunneling and orthogonality catastrophe in the topological mechanism of superconductivity
We compute the angular dependence of the order parameter and tunneling
amplitude in a model exhibiting topological superconductivity and sketch its
derivation as a model of a doped Mott insulator. We show that ground states
differing by an odd number of particles are orthogonal and the order parameter
is in the d-representation, although the gap in the electronic spectrum has no
nodes. We also develop an operator algebra, that allowes one to compute
off-diagonal correlation functions.Comment: 4 pages, Revtex, psfig; some references are correcte
Competition of Dimerization and Charge Ordering in the Spin-Peierls State of Organic Conductors
The effect of the charge ordering on the spin-Peierls (SP) state has been
examined by using a Peierls-Hubbard model at quarter-filling with dimerization,
on-site and nearest-neighbor repulsive interactions. By taking account of the
presence of dimerization, a bond distortion is calculated variationally with
the renormalization group method based on bosonization. When the charge
ordering appears at V=V_c with increasing the nearest-neighbor interaction (V),
the distortion exhibits a maximum due to competition between the dimerization
and the charge ordering. It is shown that the second-order phase transition
occurs from the SP state with the bond alternation to a mixed state with an
additional component of the site alternationat V = V_c.Comment: 11 pages, 13 figures, to be published in J. Phys. Soc. Jpn. 72 No.6
(2003
Ultrafast Hole Trapping and Relaxation Dynamics in p-Type CuS Nanodisks
CuS nanocrystals are potential materials for developing low-cost solar energy conversion devices. Understanding the underlying dynamics of photoinduced carriers in CuS nanocrystals is essential to improve their performance in these devices. In this work, we investigated the photoinduced hole dynamics in CuS nanodisks (NDs) using the combination of transient optical (OTA) and X-ray (XTA) absorption spectroscopy. OTA results show that the broad transient absorption in the visible region is attributed to the photoinduced hot and trapped holes. The hole trapping process occurs on a subpicosecond time scale, followed by carrier recombination (~100 ps). The nature of the hole trapping sites, revealed by XTA, is characteristic of S or organic ligands on the surface of CuS NDs. These results not only suggest the possibility to control the hole dynamics by tuning the surface chemistry of CuS but also represent the first time observation of hole dynamics in semiconductor nanocrystals using XTA
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