2,673 research outputs found
Three-orbital study on the orbital distillation effect in the high Tc cuprates
Our recent study has revealed that the mixture of the dz2 orbital component
into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have
also shown that applying hydrostatic pressure enhances Tc due to smaller mixing
of the Cu4s component. We call these the "orbital distillation" effect. In our
previous study, the 4s orbital was taken into account through the hoppings in
the dx2-y2 sector, but here we consider a model in which of the dx2-y2, dz2 and
4s orbitals are all considered explicitly. The present study reinforces our
conclusion that smaller 4s hybridization further enhances Tc.Comment: 4 pages, 2 figures, submitted as a proceeding of ISS2012(Tokyo
Self-Reduction Rate of a Microtubule
We formulate and study a quantum field theory of a microtubule, a basic
element of living cells. Following the quantum theory of consciousness by
Hameroff and Penrose, we let the system to reduce to one of the classical
states without measurement if certain conditions are
satisfied(self-reductions), and calculate the self-reduction time (the
mean interval between two successive self-reductions) of a cluster consisting
of more than neighboring tubulins (basic units composing a microtubule).
is interpreted there as an instance of the stream of consciousness. We
analyze the dependence of upon and the initial conditions, etc.
For relatively large electron hopping amplitude, obeys a power law
, which can be explained by the percolation theory. For
sufficiently small values of the electron hopping amplitude, obeys an
exponential law, . By using this law, we estimate the
condition for to take realistic values
\raisebox{-0.5ex}{} sec as \raisebox{-0.5ex}
{} 1000.Comment: 7 pages, 9 figures, Extended versio
Field-angle Dependence of the Zero-Energy Density of States in the Unconventional Heavy-Fermion Superconductor CeCoIn5
Field-angle dependent specific heat measurement has been done on the
heavy-fermion superconductor CeCoIn5 down to ~ 0.29 K, in a magnetic field
rotating in the tetragonal c-plane. A clear fourfold angular oscillation is
observed in the specific heat with the minima (maxima) occurring along the
[100] ([110]) directions. Oscillation persists down to low fields H << Hc2,
thus directly proving the existence of gap nodes. The results indicate that the
superconducting gap symmetry is most probably of dxy type.Comment: 8 pages, 3 figures, to be published in J. Phys. Condens. Matte
Metamagnetic Quantum Criticality Revealed by 17O-NMR in the Itinerant Metamagnet Sr3Ru2O7
We have investigated the spin dynamics in the bilayered perovskite Sr3Ru2O7
as a function of magnetic field and temperature using 17O-NMR. This system sits
close to a metamagnetic quantum critical point (MMQCP) for the field
perpendicular to the ruthenium oxide planes. We confirm Fermi-liquid behavior
at low temperatures except for a narrow field region close to the MMQCP. The
nuclear spin-lattice relaxation rate divided by temperature 1/T1T is enhanced
on approaching the metamagnetic critical field of 7.9 T and at the critical
field 1/T1T continues to increase and does not show Fermi- liquid behavior down
to 0.3 K. The temperature dependence of T1T in this region suggests the
critical temperature Theta to be 0 K, which is a strong evidence that the spin
dynamics possesses a quantum critical character. Comparison between uniform
susceptibility and 1/T1T reveals that antiferromagnetic fluctuations instead of
two-dimensional ferromagnetic fluctuations dominate the spin fluctuation
spectrum at the critical field, which is unexpected for itinerant
metamagnetism.Comment: 5 pages, 4 figures, Accepted by Phys. Rev. Let
Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRuGe
e have investigated the magnetic properties of YbRuGe by means of
magnetic susceptibility (T), specific heat C(T) and electrical
resistivity (T) measurements performed on flux grown single crystals. The
Curie-Weiss behavior of (T) along the easy plane, the large magnetic
entropy at low temperatures and the weak Kondo like increase in (T)
proves a stable trivalent Yb state. Anomalies in C(T), (T) and (T)
at T = 10.2 K, T = 6.5 K and T = 5.7 K evidence complex
ordering phenomena, T being larger than the highest Yb magnetic ordering
temperature found up to now. The magnetic entropy just above T amounts to
almost Rln4, indicating that the crystal electric field (CEF) ground state is a
quasiquartet instead of the expected doublet. The behavior at T is rather
unusual and suggest that this transition is related to quadrupolar ordering,
being a consequence of the CEF quasiquartet ground state. The combination of a
quasiquartet CEF ground state, a high ordering temperature, and the relevance
of quadrupolar interactions makes YbRuGe a rather unique system
among Yb based compounds.Comment: 11 pages, 5 figure, submitted to PRB rapi
Sign reversal of field-angle resolved heat capacity oscillations in a heavy fermion superconductor CeCoIn and pairing symmetry
To identify the superconducting gap symmetry in CeCoIn5 (Tc=2.3 K), we
performed angle-resolved specific heat (C_\phi) measurements in a field rotated
around the c-axis down to very low temperatures 0.05Tc and detailed theoretical
calculations. In a field of 1 T, a sign reversal of the fourfold angular
oscillation in C_\phi has been observed at T ~ 0.1Tc on entering a
quasiclassical regime where the maximum of C_\phi corresponds to the antinodal
direction, coinciding with the angle-resolved density of states (ADOS)
calculation. The C_\phi behavior, which exhibits minima along [110] directions,
unambiguously allows us to conclude d_{x^2-y^2} symmetry of this system. The
ADOS-quasiclassical region is confined to a narrow T and H domain within T/Tc ~
0.1 and 1.5 T (0.13Hc2).Comment: 4 pages, 4 figure
Measurement of temperature field of a Rayleigh-Bénard convection using two-color laser-induced fluorescence
The two-color laser-induced fluorescence technique developed by Sakakibara and Adrian (1999) for the measurement of planar turbulent temperature fields in water has been refined to reduce the RMS error of the instantaneous measurement by an order of magnitude. The technique achieves higher sensitivity by employing two high-resolution 14-bit monochrome CCD cameras. Further refinement is achieved by post-processing the data using a convolution method that matches the degree of the image blurring of the two images. The method is demonstrated by application to turbulent Rayleigh-Bénard convection wherein the random error is shown to be less than 0.17 K
- …