1,436 research outputs found
Theory of Thermal Hall Effect in Quantum Magnets
We present a theory of the thermal Hall effect in insulating quantum magnets,
where the heat current is totally carried by charge-neutral objects such as
magnons and spinons. Two distinct types of thermal Hall responses are
identified. For ordered magnets, the intrinsic thermal Hall effect for magnons
arises when certain conditions are satisfied for the lattice geometry and the
underlying magnetic order. The other type is allowed in a spin liquid which is
a novel quantum state since there is no order even at zero temperature. For
this case, the deconfined spinons contribute to the thermal Hall response due
to Lorentz force. These results offer a clear experimental method to prove the
existence of the deconfined spinons via a thermal transport phenomenon.Comment: 8 pages, 2 figures, final version to be published in Phys. Rev. Lett
with supporting online materia
Quantum Dynamics of Multiferroic Helimagnets: a Schwinger-Boson Approach
We study the quantum dynamics/fluctuation of the cycloidal helical magnet in
terms of the Schwinger boson approach. In sharp contrast to the classical
fluctuation, the quantum fluctuation is collinear in nature which gives rise to
the collinear spin density wave state slightly above the helical cycloidal
state as the temperature is lowered. Physical properties such as the reduced
elliptic ratio of the spiral, the neutron scattering and infrared absorption
spectra are discussed from this viewpoint with the possible relevance to the
quasi-one dimensional LiCuO and LiCuVO.Comment: 5 pages, 4 figure
Exact Analysis of Entanglement in Gapped Quantum Spin Chains
We investigate the entanglement properties of the valence-bond-solid states
with generic integer-spin . Using the Schwinger boson representation of the
valence-bond-solid states, the entanglement entropy, the von Neumann entropy of
a subsystem, is obtained exactly and its relationship with the usual
correlation function is clarified. The saturation value of the entanglement
entropy, , is derived explicitly and is interpreted in terms of
the edge-state picture. The validity of our analytical results and the
edge-state picture is numerically confirmed. We also propose a novel
application of the edge state as a qubit for quantum computation.Comment: 4 pages, 2 figure
Electro-spinon in one-dimensional Mott insulator
The low-energy dynamical optical response of dimerized and undimerized spin
liquid states in a one-dimensional charge transfer Mott insulator is
theoretically studied. An exact analysis is given for the low-energy asymptotic
behavior using conformal field theory for the undimerized state. In the
dimerized state, the infrared absorption due to the bound state of two
solitons, i.e, the breather mode, is predicted with an accurate estimate for
its oscillator strength, offering a way to detect experimentally the excited
singlet state. Effects of external magnetic fields are also discussed.Comment: 5 pages, 2 figures, some typos are correcte
Higher dimensional Calabi-Yau manifolds of Kummer type
Based on Cynk-Hulek method we construct complex Calabi-Yau varieties of
arbitrary dimensions using elliptic curves with automorphism of order 6. Also
we give formulas for Hodge numbers of varieties obtained from that
construction. We shall generalize result of Katsura and Sch\"utt to obtain
arbitrarily dimensional Calabi-Yau manifolds which are Zariski in any
characteristic Comment: 13 pages, 2 figure
Cross-Linguistic Tendencies and Durational Contrasts in Geminate Consonants: An Examination of Guinaang Bontok Geminates
In Guinaang Bontok, there is a phonological contrast between singletons and geminates in all consonants (/p t k / b d g m n l s w j/) (Reid 1963, 1973; Thurgood 1997). All phonological geminates except for the oral voiced stop geminates are phonetically long consonants (Reid 1963), allowing a phonological distinction which is primarily based on phonetic duration for nasals, fricatives, liquids, glides and voiceless stops. In a cross-linguistic examination of geminates (Thurgood 1993), there were more languages listed as examples for having stop and nasal geminates than for glide geminates, and it was suggested that alveolar was the cross-linguistically preferred place of articulation for geminate consonants. In this study, it was hypothesized that the cross-linguistically less common length contrasts, such as the length contrasts in glides, were phonetically less clear than the more common ones, such as contrasts between short and long stop and nasal consonants. Similarly, it was hypothesized that contrasts in the cross-linguistically common place of articulation (i.e. alveolar) is phonetically clearer than less common contrasts (e.g. velar). In order to test these hypotheses, duration measurements were conducted on single and geminate consonants in Guinaang Bontok. The average durational contrast between short and long glides was smaller than the contrast in stop and nasal consonants. The hypothesis was therefore partially supported
Universal relationship between crystallinity and irreversibility field of MgB2
The relationship between irreversibility field, Hirr, and crystallinity of
MgB2 bulks including carbon substituted samples was studied. The Hirr was found
to increase with an increase of FWHM of MgB2 (110) peak, which corresponds to
distortion of honeycomb boron sheet, and their universal correlation was
discovered even including carbon substituted samples. Excellent Jc
characteristics under high magnetic fields were observed in samples with large
FWHM of (110) due to the enhanced intraband scattering and strengthened grain
boundary flux pinning. The relationship between crystallinity and Hirr can
explain the large variation of Hirr for MgB2 bulks, tapes, single crystals and
thin films.Comment: 3 pages, 4 figures, to be published in Appl. Phys. Lett. (in press
Exact supersymmetry in the relativistic hydrogen atom in general dimensions -- supercharge and the generalized Johnson-Lippmann operator
A Dirac particle in general dimensions moving in a 1/r potential is shown to
have an exact N = 2 supersymmetry, for which the two supercharge operators are
obtained in terms of (a D-dimensional generalization of) the Johnson-Lippmann
operator, an extension of the Runge-Lenz-Pauli vector that relativistically
incorporates spin degrees of freedom. So the extra symmetry (S(2))in the
quantum Kepler problem, which determines the degeneracy of the levels, is so
robust as to accommodate the relativistic case in arbitrary dimensions.Comment: 4 pages, 1 figur
On the magic square C*-algebra of size 4
In this paper, we investigate the structure of the magic square C*-algebra (4) of size 4. We show that a certain twisted crossed product of (4) is isomorphic to the homogeneous C*-algebra 4 ( ()). Using this result, we show that (4) is isomorphic to the fixed point algebra of 4 ( ()) by a certain action. From this concrete realization of (4), we compute the K-groups of (4) and their generators
- …