210 research outputs found
Finite-size scaling of correlation functions in one-dimensional Anderson-Hubbard model
We study the one-dimensional Anderson-Hubbard model using the density-matrix
renormalization group method. The influence of disorder on the
Tomonaga-Luttinger liquid behavior is quantitatively discussed. Based on the
finite-size scaling analysis of density-density correlation functions, we find
the following results: i) the charge exponent is significantly reduced by
disorder at low filling and near half filling, ii) the localization length
decays as , where is the disorder strength,
independently of the on-site Coulomb interaction as well as band filling, and
iii) the localization length is strongly suppressed by the on-site Coulomb
interaction near half filling in association with the formation of the Mott
plateaus.Comment: 4 pages, 4 figure
Phase diagram of the one-dimensional half-filled extended Hubbard model
We study the ground state of the one-dimensional half-filled Hubbard model
with on-site (nearest-neighbor) repulsive interaction () and
nearest-neighbor hopping . In order to obtain an accurate phase diagram, we
consider various physical quantities such as the charge gap, spin gap,
Luttinger-liquid exponents, and bond-order-wave (BOW) order parameter using the
density-matrix renormalization group technique. We confirm that the BOW phase
appears in a substantial region between the charge-density-wave (CDW) and
spin-density-wave phases. Each phase boundary is determined by multiple means
and it allows us to do a cross-check to demonstrate the validity of our
estimations. Thus, our results agree quantitatively with the renormalization
group results in the weak-coupling regime (), with the
perturbation results in the strong-coupling regime (), and with
the quantum Monte Carlo results in the intermediate-coupling regime. We also
find that the BOW-CDW transition changes from continuous to first order at the
tricritical point and the BOW
phase vanishes at the critical end point .Comment: 4 pages, 5 figure
Ordered states in the Kitaev-Heisenberg model: From 1D chains to 2D honeycomb
We study the ground state of the 1D Kitaev-Heisenberg (KH) model using the
density-matrix renormalization group and Lanczos exact diagonalization methods.
We obtain a rich ground-state phase diagram as a function of the ratio between
Heisenberg ( and Kitaev () interactions. Depending on
the ratio, the system exhibits four long-range ordered states:
ferromagnetic- , ferromagnetic-, staggered-, N\'eel-, and two
liquid states: Tomonaga-Luttinger liquid and spiral-. The two Kitaev points
and are singular. The
-dependent phase diagram is similar to that for the 2D honeycomb-lattice
KH model. Remarkably, all the ordered states of the honeycomb-lattice KH model
can be interpreted in terms of the coupled KH chains. We also discuss the
magnetic structure of the K-intercalated RuCl, a potential Kitaev material,
in the framework of the 1D KH model. Furthermore, we demonstrate that the
low-lying excitations of the 1D KH Hamiltonian can be explained within the
combination of the known six-vertex model and spin-wave theory
Triplet superconductivity in coupled odd-gon rings
Shedding light on the nature of spin-triplet superconductivity has been a
long-standing quest of solid-state physics since the discovery of superfluidity
in liquid He. Nevertheless, the mechanism of spin-triplet pairing is much
less understood than that of spin-singlet pairing explained by the
Bardeen-Cooper-Schrieffer theory or even observed in high-temperature
superconductors. Here we propose a versatile mechanism for spin-triplet
superconductivity, which is mediated through a melting of macroscopic spin
polarization in weakly coupled odd-gon-unit system (e.g., triangular unit,
pentagon unit, etc). We demonstrate the application of this mechanism by
considering a new class of quasi-one-dimensional superconductors
ACrAs (A=K, Rb, and Cs). Furthermore, we derive a simple effective
Hamiltonian to easily illustrate the adaptability of the mechanism to general
coupled odd-gon-unit systems. We thus argue that materials consisting of
odd-numbered geometric units would be a prospect of spin-triplet
superconductivity.Comment: 12 pages, 5 figures + SUPPLEMENTARY INFORMATIO
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