205 research outputs found
On the Magnetic Excitation Spectra of High Tc Cu Oxides up to the Energies far above the Resonance Energy
Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy and La214 systems have been
studied. For La1.88Sr0.12CuO4, c"(q,w) have been measured up to ~30 meV and
existing data have been analyzed up to the energy w~150 meV by using the
phenomenological expression of the generalized magnetic susceptibility
c(q,w)=c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is the susceptibility of the
electrons without the exchange coupling J(q) among them. In the relatively low
energy region up to slightly above the resonance energy Er, it has been
reported by the authors' group that the expression can explain characteristics
of the q- and w-dependence of the spectra of YBa2Cu3Oy (YBCO or YBCOy). Here,
it is also pointed out that the expression can reproduce the rotation of four
incommensurate peaks of c"(q,w) within the a*-b* plane about (p/a, p/a) {or
so-called (p, p)} point by 45 degree, which occurs as w goes to the energy
region far above Er from E below Er. For La2-xSrxCuO4 and La2-xBaxCuO4,
agreements between the observed results and the calculations are less
satisfactory than for YBCO, indicating that we have to take account of the
existence of the "stripes" to consistently explain the observed c"(q,w) of
La214 system especially near x=1/8.Comment: 14 pages, 5 figure
Dispersion of Magnetic Excitations in Superconducting Optimally Doped YBa_2Cu_3O_6.95
Detailed neutron scattering measurements of YBa_2Cu_3O_6.95 found that the
resonance peak and incommensurate magnetic scattering induced by
superconductivity represent the same physical phenomenon: two dispersive
branches that converge near 41 meV and the in-plane wave-vector q_af=(pi/a,
pi/a) to form the resonance peak. One branch has a circular symmetry around
q_af and quadratic downward dispersion from ~41 meV to the spin gap of
33+-1meV. The other, of lower intensity, disperses from ~41 meV to at least 55
meV. Our results exclude a quartet of vertical incommensurate rods in q-w space
expected from spin waves produced by dynamical charge stripes as an origin of
the observed incommensurate scattering in optimally-doped YBCO.Comment: Version 3: Author change. Changes made throughout the text and minor
changes in figures, Model parameters slightly changed after a small error in
the calculation was discovere
Scalability of spin FPGA: A Reconfigurable Architecture based on spin MOSFET
Scalability of Field Programmable Gate Array (FPGA) using spin MOSFET (spin
FPGA) with magnetocurrent (MC) ratio in the range of 100% to 1000% is discussed
for the first time. Area and speed of million-gate spin FPGA are numerically
benchmarked with CMOS FPGA for 22nm, 32nm and 45nm technologies including 20%
transistor size variation. We show that area is reduced and speed is increased
in spin FPGA owing to the nonvolatile memory function of spin MOSFET.Comment: 3 pages, 7 figure
Pseudo-gap behavior in dynamical properties of high-Tc cuprates
Dynamical properties of 2D antiferromagnets with hole doping are investigated
to see the effects of short range local magnetic order on the temperature
dependence of the dynamical magnetic susceptibility. We show the pseudo-gap
like behavior of the temperature dependence of the NMR relaxation rate. We also
discuss implications of the results in relations to the observed spin gap like
behavior of low-doped copper oxide high- superconductors.Comment: 3 pages, Revtex, with 2 eps figures, to appear in J.Phys.Soc.Jpn.
Vol.67 No.
Measurement of Two-Qubit States by a Two-Island Single Electron Transistor
We solve the master equations of two charged qubits measured by a
single-electron transistor (SET) consisted of two islands. We show that in the
sequential tunneling regime the SET current can be used for reading out results
of quantum calculations and providing evidences of two-qubit entanglement,
especially when the interaction between the two qubits is weak
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