38 research outputs found
The Distinct Effects of Homogeneous Weak Disorder and Dilute Strong Scatterers on Phase Competetion in the Manganites
We study the two orbital double-exchange model in two dimensions in the
presence of antiferromagnetic (AF) superexchange, strong Jahn-Teller coupling,
and substitutional disorder. At hole doping x=0.5 we explore the `bicritical'
regime where the energy of a ferromagnetic metal and a charge and orbital
ordered (CO-OO) CE state are closely balanced, and compare the impact of weak
homogeneous disorder to that of a low density of strong scatterers. Even
moderate homogeneous disorder suppresses the CE-CO-OO phase and leads to a
glass with nanoscale correlations. Dilute strong scatterers of comparable
strength, however, convert the CE-CO-OO phase to a phase separated state with
ferromagnetic and AF-CO-OO clusters. We provide the first spatial description
of these phenomena and compare our results in detail to experiments on the
half-doped manganites.Comment: 4 pages pdflatex, 4 jpg figs, publishe
Memory efficient Fock-space recursion scheme for computing many-fermion resolvents
A fundamental roadblock to the exact numerical solution of many-fermion
problems is the exponential growth of the Hilbert space with system size. It
manifests as extreme dynamical memory and computation-time requirements for
simulating many-fermion processes. Here we construct a novel reorganization of
the Hilbert space to establish that the exponential growth of dynamical-memory
requirement is suppressed inversely with system size in our approach.
Consequently, the state-of-the-art resolvent computation can be performed with
substantially less memory. The memory-efficiency does not rely on Hamiltonian
symmetries, sparseness, or boundary conditions and requires no additional
memory to handle long-range density-density interaction and hopping. We provide
examples calculations of interacting fermion ground state energy, the
many-fermion density of states and few-body excitations in interacting ground
states in one and two dimensions
Adiabatic charge pumping through a dot at the junction of N quantum wires
We study adiabatic charge pumping through a quantum dot placed at the
junction of quantum wires. We explicitly map out the pattern of pumped
charge as a function of the time-varying tunneling parameters coupling the
wires to the dot and the phase between any two time varying parameters
controlling the shape of the dot. We find that with time-independent
well-coupled leads, the maximum pumped charge in the remaining two leads is
strongly suppressed with increasing , leading to the possibility of tuning
of the pumped charge, by modulating the coupling of the leads.Comment: 5 pages, 6 figures, version to be published in PR