16,608 research outputs found
Weakly coupled quantum spin singlets in BaCrO
Using single crystal inelastic neutron scattering with and without
application of an external magnetic field and powder neutron diffraction, we
have characterized magnetic interactions in BaCrO. Even without
field, we found that there exist three singlet-to-triplet excitation modes in
scattering plane. Our complete analysis shows that the three modes
are due to spatially anisotropic interdimer interactions that are induced by
local distortions of the tetrahedron of oxygens surrounding the Jahn-Teller
active Cr. The strong intradimer coupling of meV
and weak interdimer interactions ( meV) makes
BaCrO a good model system for weakly-coupled quantum spin
dimers
Scaling Relation for Excitation Energy Under Hyperbolic Deformation
We introduce a one-parameter deformation for one-dimensional (1D) quantum
lattice models, the hyperbolic deformation, where the scale of the local energy
is proportional to cosh lambda j at the j-th site. Corresponding to a 2D
classical system, the deformation does not strongly modify the ground state. In
this situation, the effective Hamiltonian of the quantum system shows that the
quasi particle is weakly bounded around the center of the system. By analyzing
this binding effect, we derive scaling relations for the mean-square width
of confinement, the energy correction with respect to the excitation gap
\Delta, and the deformation parameter . This finite-size scaling
allows us to investigate excitation gap of 1D non-deformed bulk quantum
systems.Comment: 9 pages, 5 figure
Recent advances in understanding of various chronic pain mechanisms through lysophosphatidic acid (LPA) receptor signaling
Long-range and selective coupler for superconducting flux qubits
We propose a qubit-qubit coupling scheme for superconducting flux quantum
bits (qubits), where a quantized Josephson junction resonator and microwave
irradiation are utilized. The junction is used as a tunable inductance
controlled by changing the bias current flowing through the junction, and thus
the circuit works as a tunable resonator. This enables us to make any qubits
interact with the resonator. Entanglement between two of many qubits whose
level splittings satisfy some conditions, is formed by microwave irradiation
causing a two-photon Rabi oscillation. Since the size of the resonator can be
as large as sub-millimeters and qubits interact with it via mutual inductance,
our scheme makes it possible to construct a quantum gate involving remote
qubitsComment: 8 pages, 4 figure
Infrared phonons and specific heat in Ba3Cr2O8
We report on the phonon spectrum of Ba3Cr2O8 determined by infrared
spectroscopy, and on specific heat measurements across the Jahn-Teller
transition in magnetic fields up to 9 T. Phonon modes split below the
Jahn-Teller transition, which occurs at T_{JT} = 70 K as detected by specific
heat measurements. The field-dependent specific heat data is analyzed in terms
of the contributions from lattice, magnetic and orbital degrees of freedom. In
contrast to the isostructural compound Sr3Cr2O8 our analysis does not indicate
the existence of orbital fluctuations below the Jahn-Teller transition in
Ba3Cr2O8.Comment: 5 pages, 4 figure
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