14,992 research outputs found
Effect of zero energy bound states on macroscopic quantum tunneling in high-Tc superconductor junctions
The macroscopic quantum tunneling (MQT) in the current biased high-Tc
superconductor Josephson junctions and the effect of the zero energy bound
states (ZES) on the MQT are theoretically investigated. We obtained the
analytical formula of the MQT rate and showed that the presence of the ZES at
the normal/superconductor interface leads to a strong Ohmic quasiparticle
dissipation. Therefore, the MQT rate is noticeably inhibited in compared with
the c-axis junctions in which the ZES are completely absent.Comment: 4 pages, 1 figure, comment and reference about recent experiment
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Coherent quasi-particles-to-incoherent hole-carriers crossover in underdoped cuprates
In underdoped cuprates, only a portion of the Fermi surface survives as Fermi
arcs due to pseudogap opening. In hole-doped LaCuO, we have deduced
the "coherence temperature" of quasi-particles on the Fermi arc above
which the broadened leading edge position in angle-integrated photoemission
spectra is shifted away from the Fermi level and the quasi-particle concept
starts to lose its meaning. is found to rapidly increase with hole
doping, an opposite behavior to the pseudogap temperature . The
superconducting dome is thus located below both and , indicating
that the superconductivity emerges out of the coherent Fermionic
quasi-particles on the Fermi arc. remains small in the underdoped
region, indicating that incoherent charge carriers originating from the Fermi
arc are responsible for the apparently metallic transport at high temperatures
Non-Hermitian quantum mechanics: the case of bound state scattering theory
Excited bound states are often understood within scattering based theories as
resulting from the collision of a particle on a target via a short-range
potential. We show that the resulting formalism is non-Hermitian and describe
the Hilbert spaces and metric operator relevant to a correct formulation of
such theories. The structure and tools employed are the same that have been
introduced in current works dealing with PT-symmetric and quasi-Hermitian
problems. The relevance of the non-Hermitian formulation to practical
computations is assessed by introducing a non-Hermiticity index. We give a
numerical example involving scattering by a short-range potential in a Coulomb
field for which it is seen that even for a small but non-negligible
non-Hermiticity index the non-Hermitian character of the problem must be taken
into account. The computation of physical quantities in the relevant Hilbert
spaces is also discussed
Magnetic coupling in highly-ordered NiO/Fe3O4(110): Ultrasharp magnetic interfaces vs. long-range magnetoelastic interactions
We present a laterally resolved X-ray magnetic dichroism study of the
magnetic proximity effect in a highly ordered oxide system, i.e. NiO films on
Fe3O4(110). We found that the magnetic interface shows an ultrasharp
electronic, magnetic and structural transition from the ferrimagnet to the
antiferromagnet. The monolayer which forms the interface reconstructs to
NiFe2O4 and exhibits an enhanced Fe and Ni orbital moment, possibly caused by
bonding anisotropy or electronic interaction between Fe and Ni cations. The
absence of spin-flop coupling for this crystallographic orientation can be
explained by a structurally uncompensated interface and additional
magnetoelastic effects
Physical Origin of the Boson Peak Deduced from a Two-Order-Parameter Model of Liquid
We propose that the boson peak originates from the (quasi-) localized
vibrational modes associated with long-lived locally favored structures, which
are intrinsic to a liquid state and are randomly distributed in a sea of
normal-liquid structures. This tells us that the number density of locally
favored structures is an important physical factor determining the intensity of
the boson peak. In our two-order-parameter model of the liquid-glass
transition, the locally favored structures act as impurities disturbing
crystallization and thus lead to vitrification. This naturally explains the
dependence of the intensity of the boson peak on temperature, pressure, and
fragility, and also the close correlation between the boson peak and the first
sharp diffraction peak (or prepeak).Comment: 5 pages, 1 figure, An error in the reference (Ref. 7) was correcte
Andreev bound states and tunneling characteristics of a non-centrosymmetric superconductor
The tunneling characteristics of planar junctions between a normal metal and
a non-centrosymmetric superconductor like CePt3Si are examined. It is shown
that the superconducting phase with mixed parity can give rise to
characteristic zero-bias anomalies in certain junction directions. The origin
of these zero-bias anomalies are Andreev bound states at the interface. The
tunneling characteristics for different directions allow to test the structure
of the parity-mixed pairing state.Comment: 4 pages, 3 figure
Multiphoton transitions in a macroscopic quantum two-state system
We have observed multiphoton transitions between two macroscopic
quantum-mechanical superposition states formed by two opposite circulating
currents in a superconducting loop with three Josephson junctions. Resonant
peaks and dips of up to three-photon transitions were observed in spectroscopic
measurements when the system was irradiated with a strong RF-photon field. The
widths of the multiphoton absorption dips are shown to scale with the Bessel
functions in agreement with theoretical predictions derived from the Bloch
equation or from a spin-boson model.Comment: 4 pages, 3 figure
Oblique triangular antiferromagnetic phase in CsCuCoCl
The spin-1/2 stacked triangular antiferromagnet CsCuCoCl with
undergoes two phase transitions at zero field. The
low-temperature phase is produced by the small amount of Co doping. In
order to investigate the magnetic structures of the two ordered phases, the
neutron elastic scattering experiments have been carried out for the sample
with . It is found that the intermediate phase is identical to
the ordered phase of CsCuCl, and that the low-temperature phase is an
oblique triangular antiferromagnetic phase in which the spins form a triangular
structure in a plane tilted from the basal plane. The tilting angle which is
42 at K decreases with increasing temperature, and becomes
zero at K. An off-diagonal exchange term is proposed as the
origin of the oblique phase.Comment: 6 pages, 7 figure
Hamiltonian Determination with Restricted Access in Transverse Field Ising Chain
We propose a method to evaluate parameters in the Hamiltonian of the Ising
chain under site-dependent transverse fields, with a proviso that we can
control and measure one of the edge spins only. We evaluate the eigenvalues of
the Hamiltonian and the time-evoultion operator exactly for a 3-spin chain,
from which we obtain the expectation values of of the first spin.
The parameters are found from the peak positions of the Fourier transform of
the expectation value. There are four assumptions in our method, which are mild
enough to be satisfied in many physical systems.Comment: 15pages, 4 figure
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