3,838 research outputs found
Transition from a Tomonaga-Luttinger liquid to a Fermi liquid in potassium intercalated bundles of single wall carbon nanotubes
We report on the first direct observation of a transition from a
Tomonaga-Luttinger liquid to a Fermi liquid behavior in potassium intercalated
mats of single wall carbon nanotubes (SWCNT). Using high resolution
photoemission spectroscopy an analysis of the spectral shape near the Fermi
level reveals a Tomonaga-Luttinger liquid power law scaling in the density of
states for the pristine sample and for low dopant concentration. As soon as the
doping is high enough to fill bands of the semiconducting tubes a distinct
transition to a bundle of only metallic SWCNT with a scaling behavior of a
normal Fermi liquid occurs. This can be explained by a strong screening of the
Coulomb interaction between charge carriers and/or an increased hopping matrix
element between the tubes.Comment: 5 pages, 4 figure
Transverse field effect in graphene ribbons
It is shown that a graphene ribbon, a ballistic strip of carbon monolayer,
may serve as a quantum wire whose electronic properties can be continuously and
reversibly controlled by an externally applied transverse voltage. The electron
bands of armchair-edge ribbons undergo dramatic transformations: The Fermi
surface fractures, Fermi velocity and effective mass change sign, and
excitation gaps are reduced by the transverse field. These effects are manifest
in the conductance plateaus, van Hove singularities, thermopower, and activated
transport. The control over one-dimensional bands may help enhance effects of
electron correlations, and be utilized in device applications.Comment: 4 pages, 3 figure
Comparison of Power Dependence of Microwave Surface Resistance of Unpatterned and Patterned YBCO Thin Film
The effect of the patterning process on the nonlinearity of the microwave
surface resistance of YBCO thin films is investigated. With the use of a
sapphire dielectric resonator and a stripline resonator, the microwave of
YBCO thin films was measured before and after the patterning process, as a
function of temperature and the rf peak magnetic field in the film. The
microwave loss was also modeled, assuming a dependence of
on current density . Experimental and modeled results
show that the patterning has no observable effect on the microwave residual
or on the power dependence of .Comment: Submitted to IEEE Trans. MT
Universal Features of Quantized Thermal Conductance of Carbon Nanotubes
The universal features of quantized thermal conductance of carbon nanotubes
(CNTs) are revealed through theoretical analysis based on the Landauer theory
of heat transport. The phonon-derived thermal conductance of semiconducting
CNTs exhibits a universal quantization in the low temperature limit,
independent of the radius or atomic geometry. The temperature dependence
follows a single curve given in terms of temperature scaled by the phonon
energy gap. The thermal conductance of metallic CNTs has an additional
contribution from electronic states, which also exhibits quantized behavior up
to room temperature.Comment: 4 pages, 5 figures. accepted for publication in Phys. Rev. Let
Peculiar Width Dependence of the Electronic Property of Carbon Nanoribbons
Nanoribbons (nanographite ribbons) are carbon systems analogous to carbon
nanotubes. We characterize a wide class of nanoribbons by a set of two integers
, and then define the width in terms of and . Electronic
properties are explored for this class of nanoribbons. Zigzag (armchair)
nanoribbons have similar electronic properties to armchair (zigzag) nanotubes.
The band gap structure of nanoribbons exhibits a valley structure with
stream-like sequences of metallic or almost metallic nanoribbons. These
sequences correspond to equi-width curves indexed by . We reveal a peculiar
dependence of the electronic property of nanoribbons on the width .Comment: 8 pages, 13 figure
High field electro-thermal transport in metallic carbon nanotubes
We describe the electro-thermal transport in metallic carbon nanotubes
(m-CNTs) by a semi-classical approach that takes into account the high-field
dynamical interdependence between charge carrier and phonon populations. Our
model is based on the self-consistent solution of the Boltzmann transport
equation and the heat equation mediated by a phonon rate equation that accounts
for the onset of non-equilibrium (optical) phonons in the high-field regime.
Given the metallic nature of the nanostructures, a key ingredient of the model
is the assumption of local thermalization of charge carriers. Our theory
remarkably reproduces the room temperature electrical characteristics of m-CNTs
on substrate and free standing (suspended), shedding light on charge-heat
transport in these one dimensional nanostructures. In particular, the negative
differential resistance observed in suspended m-CNTs under electric stress is
attributed to inhomogeneous field profile induced by self-heating rather than
the presence of hot phonons.Comment: 10 pages, 10 figure
Phase Diagrams of Bi1-xSbx Thin Films with Different Growth Orientations
A closed-form model is developed to evaluate the band-edge shift caused by
quantum confinement for a two-dimensional non-parabolic carrier-pocket. Based
on this model, the symmetries and the band-shifts of different carrier-pockets
are evaluated for BiSb thin films that are grown along different crystalline
axes. The phase diagrams for the BiSb thin film systems with different growth
orientations are calculated and analyzed
- …