292 research outputs found
Kondo Physics and Exact Solvability of Double Dots Systems
We study two double dot systems, one with dots in parallel and one with dots
in series, and argue they admit an exact solution via the Bethe ansatz. In the
case of parallel dots we exploit the exact solution to extract the behavior of
the linear response conductance. The linear response conductance of the
parallel dot system possesses multiple Kondo effects, including a Kondo effect
enhanced by a nonpertubative antiferromagnetic RKKY interaction, has
conductance zeros in the mixed valence regime, and obeys a non-trivial form of
the Friedel sum rule.Comment: 4 pages, 2 figures; v2: published form to appear in August 2007 issue
of Phys. Rev. Let
Massless Boundary Sine-Gordon at the Free Fermion Point: Correlation and Partition Functions with Applications to Quantum Wires
In this report we compute the boundary states (including the boundary
entropy) for the boundary sine-Gordon theory. From the boundary states, we
derive both correlation and partition functions. Through the partition
function, we show that boundary sine-Gordon maps onto a doubled boundary Ising
model. With the current-current correlators, we calculate for finite system
size the ac-conductance of tunneling quantum wires with dimensionless free
conductance 1/2 (or, alternatively interacting quantum Hall edges at filling
fraction 1/2). In the dc limit, the results of C. Kane and M. Fisher, Phys.
Rev. B46 (1992) 15233, are reproduced.Comment: 24 pages; Tex with harvmac macros; 4 Postscript figures, uuencode
A Renormalization Group For Treating 2D Coupled Arrays of Continuum 1D Systems
We study the spectrum of two dimensional coupled arrays of continuum
one-dimensional systems by wedding a density matrix renormalization group
procedure to a renormalization group improved truncated spectrum approach. To
illustrate the approach we study the spectrum of large arrays of coupled
quantum Ising chains. We demonstrate explicitly that the method can treat the
various regimes of chains, in particular the three dimensional Ising ordering
transition the chains undergo as a function of interchain coupling.Comment: 5 pages, 4 figure
Exciton Hierarchies in Gapped Carbon Nanotubes
We present evidence that the strong electron-electron interactions in gapped
carbon nanotubes lead to finite hierarchies of excitons within a given nanotube
subband. We study these hierarchies by employing a field theoretic reduction of
the gapped carbon nanotube permitting electron-electron interactions to be
treated exactly. We analyze this reduction by employing a Wilsonian-like
numerical renormalization group. We are so able to determine the gap ratios of
the one-photon excitons as a function of the effective strength of
interactions. We also determine within the same subband the gaps of the
two-photon excitons, the single particle gaps, as well as a subset of the dark
excitons. The strong electron-electron interactions in addition lead to
strongly renormalized dispersion relations where the consequences of
spin-charge separation can be readily observed.Comment: 8 pages, 4 figure
Orbital Dependence of Quasiparticle Lifetimes in Sr2RuO4
Using a phenomenological Hamiltonian, we investigate the quasiparticle
lifetimes and dispersions in the three low energy bands, gamma, beta, and alpha
of Sr2RuO4. Couplings in the Hamiltonian are fixed so as to produce the mass
renormalization as measured in magneto-oscillation experiments. We thus find
reasonable agreement in all bands between our computed lifetimes and those
measured in ARPES experiments by Kidd et al. [1] and Ingle et al. [2]. In
comparing computed to measured quasiparticle dispersions, we however find good
agreement in the alpha-band alone.Comment: 7 pages, 5 figure
Tree tensor networks and entanglement spectra
A tree tensor network variational method is proposed to simulate quantum
many-body systems with global symmetries where the optimization is reduced to
individual charge configurations. A computational scheme is presented, how to
extract the entanglement spectra in a bipartite splitting of a loopless tensor
network across multiple links of the network, by constructing a matrix product
operator for the reduced density operator and simulating its eigenstates. The
entanglement spectra of 2 x L, 3 x L and 4 x L with either open or periodic
boundary conditions on the rungs are studied using the presented methods, where
it is found that the entanglement spectrum depends not only on the subsystem
but also on the boundaries between the subsystems.Comment: 16 pages, 16 figures (20 PDF figures
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