663 research outputs found
Topological quantum phase transition in the BEC-BCS crossover phenomena
A crossover between the Bose Einstein condensation (BEC) and BCS
superconducting state is described topologically in the chiral symmetric
fermion system with attractive interaction. Using a local Z_2 Berry phase, we
found a quantum phase transition between the BEC and BCS phases without
accompanying the bulk gap closing.Comment: 4 pages, 5 figure
Exact spin dynamics of the 1/r^2 supersymmetric t-J model in a magnetic field
The dynamical spin structure factor S^{zz}(Q,omega) in the small momentum
region is derived analytically for the one-dimensional supersymmetric t-J model
with 1/r^2 interaction. Strong spin-charge separation is found in the spin
dynamics. The structure factor S^{zz}(Q,omega) with a given spin polarization
does not depend on the electron density in the small momentum region. In the
thermodynamic limit, only two spinons and one antispinon (magnon) contribute to
S^{zz}(Q,omega). These results are derived via solution of the SU(2,1)
Sutherland model in the strong coupling limit.Comment: 20 pages, 8 figures. Accepted for publication in J.Phys.
Basic properties of three-leg Heisenberg tube
We study three-leg antiferromagnetic Heisenberg model with the periodic
boundary conditions in the rung direction. Since the rungs form regular
triangles, spin frustration is induced. We use the density-matrix
renormalization group method to investigate the ground state. We find that the
spin excitations are always gapped to remove the spin frustration as long as
the rung coupling is nonzero. We also visibly confirm spin-Peierls dimerization
order in the leg direction. Both the spin gap and the dimerization order are
basically enhanced as the rung coupling increases.Comment: 4 pages, 2 figure
Derivation of Green's Function of Spin Calogero-Sutherland Model by Uglov's Method
Hole propagator of spin 1/2 Calogero-Sutherland model is derived using
Uglov's method, which maps the exact eigenfunctions of the model, called
Yangian Gelfand-Zetlin basis, to a limit of Macdonald polynomials (gl_2-Jack
polynomials). To apply this mapping method to the calculation of 1-particle
Green's function, we confirm that the sum of the field annihilation operator on
Yangian Gelfand-Zetlin basis is transformed to the field annihilation operator
on gl_2-Jack polynomials by the mapping. The resultant expression for hole
propagator for finite-size system is written in terms of renormalized momenta
and spin of quasi-holes and the expression in the thermodynamic limit coincides
with the earlier result derived by another method. We also discuss the
singularity of the spectral function for a specific coupling parameter where
the hole propagator of spin Calogero-Sutherland model becomes equivalent to
dynamical colour correlation function of SU(3) Haldane-Shastry model.Comment: 36 pages, 8 figure
Dynamical visualization of anisotropic electromagnetic re-emissions from a single metal micro-helix at THz frequencies
微小金属らせんとテラヘルツ光との相互作用を可視化 --次世代超高速移動通信などにおける高性能アンテナへ応用--. 京都大学プレスリリース. 2021-02-09.The capability for actual measurements—not just simulations—of the dynamical behavior of THz electromagnetic waves, including interactions with prevalent 3D objects, has become increasingly important not only for developments of various THz devices, but also for reliable evaluation of electromagnetic compatibility. We have obtained real-time visualizations of the spatial evolution of THz electromagnetic waves interacting with a single metal micro-helix. After the micro-helix is stimulated by a broadband pico-second pulse of THz electromagnetic waves, two types of anisotropic re-emissions can occur following overall inductive current oscillations in the micro-helix. They propagate in orthogonally crossed directions with different THz frequency spectra. This unique radiative feature can be very useful for the development of a smart antenna with broadband multiplexing/demultiplexing ability and directional adaptivity. In this way, we have demonstrated that our advanced measurement techniques can lead to the development of novel functional THz devices
"Hot Electron Spectra in Plain, Cone and Integrated Targets for FIREX-I Using Electron Spectrometer"
Atomic Carbon and CO Isotope Emission in the Vicinity of DR15
We present observations of the 3P1-3P0 fine structure transition of atomic
carbon [CI], the J=3-2 transition of CO, as well as of the J=1-0 transitions of
13CO and C18O toward DR15, an HII region associated with two mid-infrared dark
clouds (IRDCs). The 13CO and C18O J=1-0 emissions closely follow the dark
patches seen in optical wavelength, showing two self-gravitating molecular
cores with masses of 2000 Msun and 900 Msun, respectively, at the positions of
the catalogued IRDCs.
Our data show a rough spatial correlation between [CI] and 13CO J=1-0. Bright
[CI] emission occurs in relatively cold gas behind the molecular cores, neither
in highly excited gas traced by CO J=3-2 emission nor in HII region/molecular
cloud interface. These results are inconsistent with those predicted by
standard photodissociation region (PDR) models, suggesting an origin for
interstellar atomic carbon unrelated to photodissociation processes.Comment: 11 pages Latex, 6 figures, Accepted for publication in The
Astrophysical Journa
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