4 research outputs found
Proximity to a Nearly Superconducting Quantum Critical Liquid
The coupling between superconductors and a quantum critical liquid that is
nearly superconducting provides natural interpretation for the Josephson effect
over unexpectedly long junctions, and the remarkable stripe-spacing dependence
of the critical temperature in LSCO and YBCO superconductors.Comment: four two-column pages, no figure
Supersymmetry in carbon nanotubes in a transverse magnetic field
Electron properties of Carbon nanotubes in a transverse magnetic field are
studied using a model of a massless Dirac particle on a cylinder. The problem
possesses supersymmetry which protects low energy states and ensures stability
of the metallic behavior in arbitrarily large fields. In metallic tubes we find
suppression of the Fermi velocity at half-filling and enhancement of the
density of states. In semiconducting tubes the energy gap is suppressed. These
features qualitatively persist (although to a smaller degree) in the presence
of electron interactions. The possibilities of experimental observation of
these effects are discussed.Comment: A new section on electron interaction effects added and explanation
on roles of supersymmetry expanded. Revtex4, 6 EPS figure file
W=0 Pairing in Carbon Nanotubes away from Half Filling
We use the Hubbard Hamiltonian on the honeycomb lattice to represent the
valence bands of carbon single-wall nanotubes. A detailed symmetry
analysis shows that the model allows W=0 pairs which we define as two-body
singlet eigenstates of with vanishing on-site repulsion. By means of a
non-perturbative canonical transformation we calculate the effective
interaction between the electrons of a W=0 pair added to the interacting ground
state. We show that the dressed W=0 pair is a bound state for resonable
parameter values away from half filling. Exact diagonalization results for the
(1,1) nanotube confirm the expectations. For nanotubes of length ,
the binding energy of the pair depends strongly on the filling and decreases
towards a small but nonzero value as . We observe the existence
of an optimal doping when the number of electrons per C atom is in the range
1.21.3, and the binding energy is of the order of 0.1 1 meV.Comment: 16 pages, 6 figure
Theoretical STM signatures and transport properties of native defects in carbon nanotubes
Article on theoretical STM signatures and transport properties of native defects in carbon nanotubes