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 LiCu$_2$O$_2$ and LiCuVO$_4$.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 $S$. 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, $2 \log_2 (S+1)$, 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 $p\not\equiv 1\pmod{12}.$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 ( ($\mathbb{R}$$^3$)). Using this result, we show that (4) is isomorphic to the fixed point algebra of 4 ( ($\mathbb{R}$$^3$)) by a certain action. From this concrete realization of (4), we compute the K-groups of (4) and their generators