1,753 research outputs found
Andreev Edge State on Semi-Infinite Triangular Lattice: Detecting the Pairing Symmetry in Na_0.35CoO_2.yH_2O
We study the Andreev edge state on the semi-infinite triangular lattice with
different pairing symmetries and boundary topologies. We find a rich phase
diagram of zero energy Andreev edge states that is a unique fingerprint of each
of the possible pairing symmetries. We propose to pin down the pairing symmetry
in recently discovered Na_xCoO_2 material by the Fourier-transformed scanning
tunneling spectroscopy for the edge state. A surprisingly rich phase diagram is
found and explained by a general gauge argument and mapping to 1D tight-binding
model. Extensions of this work are discussed at the end.Comment: 4 pages, 1 table, 4 figure
Electromagnetic break-up of nuclei with A = 3 - 7
This talk contains a short review of some of the progresses made in the last
three years in the calculations of electromagnetic cross sections of light
nuclei up to A=7. Since many of them have been possible thanks to the use of
the Lorentz Integral Transform (LIT) method, both for inclusive and exclusive
reactions, I will first make a few remarks on the method, stressing its
essential points and then show results for different nuclei. One of the
interesting outcomes is e.g. the appearing of typical collective motion
features from ab initio six-body calculations. When a comparison with available
experimental data is attempted, it is rather disappointing to realize that
low-energy data are old, incomplete and not accurate enough to disantangle
interesting effects, showing the need of a major experimental program in this
direction, together with more theoretical efforts to implement modern realistic
forces in continuum calculations of systems.Comment: 4 pages, 7 figures, invited talk at the FB17 - Durham (N.C) June 5-10
200
Longitudinal response function of 4He with a realistic force
The longitudinal response function of 4He is calculated with the Argonne V18
potential. The comparison with experiment suggests the need of a three-body
force. When adding the Urbana IX three-body potential in the calculation of the
lower longitudinal multipoles, the total strength is suppressed in the
quasi-elastic peak, towards the trend of the experimental data.Comment: 3 pages, 3 figures, proceedings of the 20th European Conference on
Few-Body Problems in Physics (EFB20
The effective interaction hyperspherical harmonics method for non-local potentials
A different formulation of the effective interaction hyperspherical harmonics
(EIHH) method, suitable for non-local potentials, is presented. The EIHH method
for local interactions is first shortly reviewed to point out the problems of
an extension to non-local potentials. A viable solution is proposed and, as an
application, results on the ground-state properties of 4- and 6-nucleon systems
are presented. One finds a substantial acceleration in the convergence rate of
the hyperspherical harmonics series. Perspectives for an application to
scattering cross sections, via the Lorentz transform method are discussed.Comment: 6 pages, 1 figure, to be published in the Proceedings of the
International Nuclear Physics Conference, Vancouver, 201
On the Accuracy of Hyperspherical Harmonics Approaches to Photonuclear Reactions
Using the Lorentz Integral Transform (LIT) method we compare the results for
the triton total photodisintegration cross section obtained using the
Correlated Hyperspherical Harmonics (CHH) and the Effective Interaction
Hyperspherical Harmonics (EIHH) techniques. We show that these two approaches,
while rather different both conceptually and computationally, lead to results
which coincide within high accuracy. The calculations which include two- and
three-body forces are of the same high quality in both cases. We also discuss
the comparison of the two approaches in terms of computational efficiency.
These results are of major importance in view of applications to the much
debated case of the four-nucleon photoabsorption.Comment: 12 pages, 3 figure
Berry Phase in Cuprate Superconductors
Geometrical Berry phase is recognized as having profound implications for the
properties of electronic systems. Over the last decade, Berry phase has been
essential to our understanding of new materials, including graphene and
topological insulators. The Berry phase can be accessed via its contribution to
the phase mismatch in quantum oscillation experiments, where electrons
accumulate a phase as they traverse closed cyclotron orbits in momentum space.
The high-temperature cuprate superconductors are a class of materials where the
Berry phase is thus far unknown despite the large body of existing quantum
oscillations data. In this report we present a systematic Berry phase analysis
of Shubnikov - de Haas measurements on the hole-doped cuprates
YBaCuO, YBaCuO, HgBaCuO, and the
electron-doped cuprate NdCeCuO. For the hole-doped materials, a
trivial Berry phase of 0 mod is systematically observed whereas the
electron-doped NdCeCuO exhibits a significant non-zero Berry
phase. These observations set constraints on the nature of the high-field
normal state of the cuprates and points towards contrasting behaviour between
hole-doped and electron-doped materials. We discuss this difference in light of
recent developments related to charge density-wave and broken time-reversal
symmetry states.Comment: new version with added supplementary informatio
Effect of P-wave interaction in 6He and 6Li photoabsorption
The total photoabsorption cross sections of six-body nuclei are calculated
including complete final state interaction via the Lorentz Integral Transform
method. The effect of nucleon-nucleon central P-wave forces is investigated.
Comparing to results with central potentials containg S-wave forces only one
finds considerably more strength in the low-energy cross sections and a rather
strong improvement in comparison with experimental data, in particular for 6Li.Comment: 11 pages with 4 figure
- …