14,759 research outputs found
Temperature dependence of the spin and orbital magnetization density in around the spin-orbital compensation point
Non-resonant ferromagnetic x-ray diffraction has been used to separate the
spin and orbital contribution to the magnetization density of the proposed
zero-moment ferromagnet . The alignment of the
spin and orbital moments relative to the net magnetization shows a sign
reversal at 84K, the compensation temperature. Below this temperature the
orbital moment is larger than the spin moment, and vice versa above it. This
result implies that the compensation mechanism is driven by the different
temperature dependencies of the spin and orbital moments. Specific heat
data indicate that the system remains ferromagnetically ordered throughout
Modulated Vortex Lattice in High Fields and Gap Nodes
The mean field vortex phase diagram of a quasi two dimensional superconductor
with a nodal d-wave pairing and with strong Pauli spin depairing is examined in
the parallel field case in order to examine an effect of gap nodes (or minima)
on the stability of a FFLO-like vortex lattice. We find through a heuristic
argument and a model calculation with a four-fold anisotropic Fermi velocity
that the FFLO-like state is relatively suppressed as the field approaches a
nodal direction. When taking account of a couple of experimental results
altogether, the present result strongly suggests that a node or gap minimum of
the pairing function of CeCoIn is located along the [100]-direction.Comment: 5 pages, 2 figures, References were added. To appear in Phys. Rev.
Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field
We report measurements of the temperature dependent components of the
magnetic penetration depth {\lambda}(T) in single crystal samples of
YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We
observe a downturn in {\lambda}(T) at low temperatures for currents flowing
along the b and c axes but not along the a axis. The downturn in {\lambda}_b is
suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy
of {\lambda}(T) likely result from proximity induced superconducting on the CuO
chains, however we also discuss the possibility that a significant part of the
anisotropy might originate from the CuO2 planes.Comment: 5 page
Precise measurements of electron and hole g-factors of single quantum dots by using nuclear field
We demonstrated the cancellation of the external magnetic field by the
nuclear field at one edge of the nuclear polarization bistability in single
InAlAs quantum dots. The cancellation for the electron Zeeman splitting gives
the precise value of the hole g-factor. By combining with the exciton g-factor
that is obtained from the Zeeman splitting for linearly polarized excitation,
the magnitude and sign of the electron and hole g-factors in the growth
direction are evaluated.Comment: 3 pages, 2 figure
Linear-response theory of the longitudinal spin Seebeck effect
We theoretically investigate the longitudinal spin Seebeck effect, in which
the spin current is injected from a ferromagnet into an attached nonmagnetic
metal in a direction parallel to the temperature gradient. Using the fact that
the phonon heat current flows intensely into the attached nonmagnetic metal in
this particular configuration, we show that the sign of the spin injection
signal in the longitudinal spin Seebeck effect can be opposite to that in the
conventional transverse spin Seebeck effect when the electron-phonon
interaction in the nonmagnetic metal is sufficiently large. Our linear-response
approach can explain the sign reversal of the spin injection signal recently
observed in the longitudinal spin Seebeck effect.Comment: Proc. of ICM 2012 (Accepted for publication in J. Korean Phys. Soc.),
typos correcte
Size-dependent fine-structure splitting in self-organized InAs/GaAs quantum dots
A systematic variation of the exciton fine-structure splitting with quantum
dot size in single InAs/GaAs quantum dots grown by metal-organic chemical vapor
deposition is observed. The splitting increases from -80 to as much as 520
eV with quantum dot size. A change of sign is reported for small quantum
dots. Model calculations within the framework of eight-band k.p theory and the
configuration interaction method were performed. Different sources for the
fine-structure splitting are discussed, and piezoelectricity is pinpointed as
the only effect reproducing the observed trend.Comment: 5 pages, 5 figure
S-wave bottom tetraquarks
The relativistic four-quark equations are found in the framework of
coupled-channel formalism. The dynamical mixing of the meson-meson states with
the four-quark states is considered. The four-quark amplitudes of the
tetraquarks, including , , and bottom quarks, are constructed. The
poles of these amplitudes determine the masses and widths of -wave bottom
tetraquarks.Comment: 8 pages, late
- …