10,767 research outputs found
One dimensional model for doubly degenerate electrons
A Hubbard-like model with SU(4) symmetry for electrons with two-fold orbital
degeneracy is studied extensively. Exact solution in one dimension is derived
by means of Bethe ansatz, where the sites are supposed to be occupied by at
most two electrons. The features of ground state and excited states for
repulsive coupling are shown. For finite N number of electrons, the
configurations of quantum numbers are given explicitly and the spectra of
excitations are obtained by solving the Bethe-ansatz equation numerically. For
infinite N, the ground state and various kinds of low-lying excitations are
obtained on the basis of thermodynamics limit.Comment: Revtex, 21 pages including 9 figures, PRB versio
Numerical and Monte Carlo Bethe ansatz method: 1D Heisenberg model
In this paper we present two new numerical methods for studying thermodynamic
quantities of integrable models. As an example of the effectiveness of these
two approaches, results from numerical solutions of all sets of Bethe ansatz
equations, for small Heisenberg chains, and Monte Carlo simulations in
quasi-momentum space, for a relatively larger chains, are presented. Our
results agree with those obtained by thermodynamics Bethe ansatz (TBA) and
Quantum Transfer Matrix (QTM).Comment: 8 pages, 6 figure
Cooling a nanomechanical resonator by a triple quantum dot
We propose an approach for achieving ground-state cooling of a nanomechanical
resonator (NAMR) capacitively coupled to a triple quantum dot (TQD). This TQD
is an electronic analog of a three-level atom in configuration which
allows an electron to enter it via lower-energy states and to exit only from a
higher-energy state. By tuning the degeneracy of the two lower-energy states in
the TQD, an electron can be trapped in a dark state caused by destructive
quantum interference between the two tunneling pathways to the higher-energy
state. Therefore, ground-state cooling of an NAMR can be achieved when
electrons absorb readily and repeatedly energy quanta from the NAMR for
excitations.Comment: 6 pages, 3 figure
Thermodynamics of SU(2) bosons in one dimension
On the basis of Bethe ansatz solution of two-component bosons with SU(2)
symmetry and -function interaction in one dimension, we study the
thermodynamics of the system at finite temperature by using the strategy of
thermodynamic Bethe ansatz (TBA). It is shown that the ground state is an
isospin "ferromagnetic" state by the method of TBA, and at high temperature the
magnetic property is dominated by Curie's law. We obtain the exact result of
specific heat and entropy in strong coupling limit which scales like at low
temperature. While in weak coupling limit, it is found there is still no
Bose-Einstein Condensation (BEC) in such 1D system.Comment: 7 page
Quantum state transmission in a cavity array via two-photon exchange
The dynamical behavior of a coupled cavity array is investigated when each
cavity contains a three-level atom. For the uniform and staggered intercavity
hopping, the whole system Hamiltonian can be analytically diagonalized in the
subspace of single-atom excitation. The quantum state transfer along the
cavities is analyzed in detail for distinct regimes of parameters, and some
interesting phenomena including binary transmission, selective localization of
the excitation population are revealed. We demonstrate that the uniform
coupling is more suitable for the quantum state transfer. It is shown that the
initial state of polariton located in the first cavity is crucial to the
transmission fidelity, and the local entanglement depresses the state transfer
probability. Exploiting the metastable state, the distance of the quantum state
transfer can be much longer than that of Jaynes-Cummings-Hubbard model. A
higher transmission probability and longer distance can be achieved by
employing a class of initial encodings and final decodings.Comment: 8 pages, 7 figures. to appear in Phys. Rev.
Energy Flexibility of Building Cluster – Part I: Occupancy Modelling
With the growing application of renewable energy, the stability of power systems can be seriously affected due to the fluctuations in the instantaneous generated power. As one of the potential solutions for this upcoming challenge, energy flexibility of buildings has received attention for research and technology development. Demand response and energy flexibility should be implemented at a large scale to have the accumulated energy flexibility to a magnitude, which can be meaningful for energy sectors. Studies have shown that the energy flexibility of a building is greatly influenced by both building physical characteristics and occupancy pattern of residents. To the best knowledge of authors, occupancy has not been considered in the study of building cluster. The aim of this paper is to present the modelling process of occupancy/vacancy of Danish households based on Danish Time Use Survey (DTUS) 2008/09 data. In this paper, we present a data-driven approach to generate occupancy/vacancy models for different types of household and for building cluster of different scales. As the result, vacancy profile and vacancy duration models are developed. The stochasticity of occupancy is also unveiled. The next step is to apply these models to quantify energy flexibility of building cluster and the uncertainty of energy flexibility due to the stochastic occupancy
- …