41 research outputs found
Correlated transport and non-Fermi liquid behavior in single-wall carbon nanotubes
We derive the effective low-energy theory for single-wall carbon nanotubes
including the Coulomb interactions among electrons. The generic model found
here consists of two spin-1/2 fermion chains which are coupled by the
interaction. We analyze the theory using bosonization, renormalization-group
techniques, and Majorana refermionization. Several experimentally relevant
consequences of the breakdown of Fermi liquid theory observed here are
discussed in detail, e.g., magnetic instabilities, anomalous conductance laws,
and impurity screening profiles.Comment: 23 pages REVTeX, incl 5 figs, to appear in Europ.Phys.Journal
Interaction induced dimerization in zigzag single wall carbon nanotubes
We derive a low-energy effective model of metallic zigzag carbon nanotubes at
half filling. We show that there are three important features characterizing
the low-energy properties of these systems: the long-range Coulomb interaction,
umklapp scattering and an explicit dimerization generated by interactions. The
ratio of the dimerization induced gap and the Mott gap induced by the umklapp
interactions is dependent on the radius of the nanotube and can drive the
system through a quantum phase transition with SU(2)_1 quantum symmetry. We
consider the physical properties of the phases on either side of this
transition which should be relevant for realistic nanotubes.Comment: 8 pages, 5 figure
Exact solution of the three-boson problem at vanishing energy
A zero range approach is used to model resonant two-body interactions between
three identical bosons. A dimensionless phase parametrizes the three-body
boundary condition while the scattering length enters the Bethe-Peierls
boundary condition. The model is solved exactly at zero energy for any value of
the scattering length, positive or negative. From this solution, an analytical
expression for the rate of three-body recombination to the universal shallow
dimer is extracted.Comment: 12 page
Comment on ``Enhancement of the Tunneling Density of States in Tomonaga-Luttinger Liquids''
In a recent Physical Review Letter, Oreg and Finkel'stein (OF) have
calculated the electron density of states (DOS) for tunneling into a repulsive
Luttinger liquid close to the location of an impurity. The result of their
calculation is a DOS which is enhanced with respect to the pure system, and
moreover diverging for not too strong repulsion. In this Comment we intend to
show that OF's calculation suffers from a subtle flaw which, being corrected,
results into a DOS not only vanishing at zero frequency but in fact suppressed
in comparison with the DOS of a pure Luttinger liquid.Comment: 1 page, Revte
Statistical properties of localisation--delocalisation transition in one dimension
We study a one-dimensional model of disordered electrons (also relevant for
random spin chains), which exhibits a delocalisation transition at
half-filling. Exact probability distribution functions for the Wigner time and
transmission coefficient are calculated. We identify and distinguish those
features of probability densities that are due to rare, trapping configurations
of the random potential from those which are due to the proximity to the
delocalisation transition.Comment: 4 pages, RevTeX, 1 fi
The effect of a local perturbation in a fermionic ladder
We study the effect of a local external potential on a system of two parallel
spin-polarized nanowires placed close to each other. For single channel
nanowires with repulsive interaction we find that transport properties of the
system are highly sensitive to the transverse gradient of the perturbation: the
asymmetric part completely reflects the electrons leading to vanishing
conductance at zero temperature, while the flat potential remains transparent.
We envisage a possible application of this unusual property in the sensitive
measurement of local potential field gradients.Comment: 4+ pages, 2 figures, typos correcte
Lattice defects and boundaries in conducting carbon nanotubes
We consider the effect of various defects and boundary structures on the low
energy electronic properties in conducting zigzag and armchair carbon
nanotubes. The tight binding model of the conduction bands is mapped exactly
onto simple lattice models consisting of two uncoupled parallel chains.
Imperfections such as impurities, structural defects or caps can be easily
included into the effective lattice models, allowing a detailed physical
interpretation of their consequences. The method is quite general and can be
used to study a wide range of possible imperfections in carbon nanotubes. We
obtain the electron density patterns expected from a scanning tunneling
microscopy experiment for half fullerene caps and two typical impurities in the
bulk of a tube, namely the Stone-Wales defect and a single vacancy.Comment: 15 pages and 16 figures. The latest version can be found at
http://www.physik.uni-kl.de/eggert/papers/index.htm