87 research outputs found
Spin interfaces in the Ashkin-Teller model and SLE
We investigate the scaling properties of the spin interfaces in the
Ashkin-Teller model. These interfaces are a very simple instance of lattice
curves coexisting with a fluctuating degree of freedom, which renders the
analytical determination of their exponents very difficult. One of our main
findings is the construction of boundary conditions which ensure that the
interface still satisfies the Markov property in this case. Then, using a novel
technique based on the transfer matrix, we compute numerically the left-passage
probability, and our results confirm that the spin interface is described by an
SLE in the scaling limit. Moreover, at a particular point of the critical line,
we describe a mapping of Ashkin-Teller model onto an integrable 19-vertex
model, which, in turn, relates to an integrable dilute Brauer model.Comment: 12 pages, 6 figure
Anomalous diffusion in the Long-Range Haken-Strobl-Reineker model
We analyze the propagation of excitons in a -dimensional lattice with
power-law hopping in the presence of dephasing, described
by a generalized Haken-Strobl-Reineker model. We show that in the strong
dephasing (quantum Zeno) regime the dynamics is described by a classical master
equation for an exclusion process with long jumps. In this limit, we
analytically compute the spatial distribution, whose shape changes at a
critical value of the decay exponent . The exciton
always diffuses anomalously: a superdiffusive motion is associated to a L\'evy
stable distribution with long-range algebraic tails for , while for the distribution corresponds to a
surprising mixed Gaussian profile with long-range algebraic tails, leading to
the coexistence of short-range diffusion and long-range L\'evy-flights. In the
many-exciton case, we demonstrate that, starting from a domain-wall exciton
profile, algebraic tails appear in the distributions for any , which
affects thermalization: the longer the hopping range, the faster equilibrium is
reached. Our results are directly relevant to experiments with cold trapped
ions, Rydberg atoms and supramolecular dye aggregates. They provide a way to
realize an exclusion process with long jumps experimentally.Comment: 5 pages, 2 figure
On three-point connectivity in two-dimensional percolation
We argue the exact universal result for the three-point connectivity of
critical percolation in two dimensions. Predictions for Potts clusters and for
the scaling limit below p_c are also given.Comment: 10 pages, 1 figur
Boundary conformal field theories and loop models
We propose a systematic method to extract conformal loop models for rational
conformal field theories (CFT). Method is based on defining an ADE model for
boundary primary operators by using the fusion matrices of these operators as
adjacency matrices. These loop models respect the conformal boundary
conditions. We discuss the loop models that can be extracted by this method for
minimal CFTs and then we will give dilute O(n) loop models on the square
lattice as examples for these loop models. We give also some proposals for WZW
SU(2) models.Comment: 23 Pages, major changes! title change
Hierarchical structure in the orbital entanglement spectrum in Fractional Quantum Hall systems
We investigate the non-universal part of the orbital entanglement spectrum
(OES) of the nu = 1/3 fractional quantum Hall effect (FQH) ground-state with
Coulomb interactions. The non-universal part of the spectrum is the part that
is missing in the Laughlin model state OES whose level counting is completely
determined by its topological order. We find that the OES levels of the Coulomb
interaction ground-state are organized in a hierarchical structure that mimic
the excitation-energy structure of the model pseudopotential Hamiltonian which
has a Laughlin ground state. These structures can be accurately modeled using
Jain's "composite fermion" quasihole-quasiparticle excitation wavefunctions. To
emphasize the connection between the entanglement spectrum and the energy
spectrum, we also consider the thermodynamical OES of the model pseudopotential
Hamiltonian at finite temperature. The observed good match between the
thermodynamical OES and the Coulomb OES suggests a relation between the
entanglement gap and the true energy gap.Comment: 16 pages, 19 figure
Controlled nucleation of thin microcrystalline layers for the recombination junction in a-Si stacked cells
In high-efficiency a-Si : H based stacked cells, at least one of the two layers that form the internal n/p junction has preferentially to be microcrystalline so as to obtain sufficient recombination at the junction [1â6]. The crucial point is the nucleation of a very thin ÎŒc-Si : H layer on an amorphous (i-layer) substrate [2, 4]. In this study, fast nucleation is induced through the treatment of the amorphous substrate by a CO2 plasma. The resulting n-layers with a high crystalline fraction were, however, found to reduce the Voc when incorporated in tandem cells. The reduction of the Voc could be restored only by a precise control of the crystalline fraction of the n-layer. As a technologically more feasible alternative, we propose a new, combined n-layer, consisting of a first amorphous layer for a high Voc, and a second microcrystalline layer, induced by CO2 treatment, for a sufficient recombination at the n/p junction. Resulting tandem cells show no Voc losses compared to two standard single cells, and an efficient recombination of the carriers at the internal junction as proved by the low series resistance (15 Ωcm2) and the high FF ( 75%) of the stacked cells
- âŠ