Thermoelectric properties of lanthanum sesquisulfide with Ti additive

The electrical resistivity, thermopower, and thermal conductivity have been measured for the lanthanum sesquisulfide (La2S3) of which the crystal phase is controlled by the Ti additive. In all the samples, the thermopower is negative between 300 and 1000 K. The sample with 8 wt % Ti, which consists almost of the cubic γ phase, behaves as a degenerate semiconductor. The thermoelectric figure of merit ZT increases with increasing temperature, reaching a value of 0.21 at 1000 K. In contrast, the sample with 2 wt % Ti consists almost of the tetragonal β phase. The transport mechanism can be well explained by the model of the Anderson localization. The ZT value increases abruptly with increasing temperature. At 1000 K, this ZT value is comparable with that of the sample with 8 wt % Ti

Geometric Engineering of Seiberg-Witten Theories with Massive Hypermultiplets

We analyze the geometric engineering of the N=2 SU(2) gauge theories with $1\leq N_f\leq 3$ massive hypermultiplets in the vector representation. The set of partial differential equations satisfied by the periods of the Seiberg-Witten differential is obtained from the Picard-Fuchs equations of the local B-model. The differential equations and its solutions are consistent with the massless case. We show that the Yukawa coupling of the local A-model gives rise to the correct instanton expansion in the gauge theory, and propose the pattern of the distribution of the world-sheet instanton number from it. As a side result, we obtain the asymptotic form of the instanton number in the gauge theories with massless hypermultiplets.Comment: 35 pages, 3 figures, (v2) clarifying comments, additional reference

Extreme Asymmetry in the Disk of V1247 Ori

We present the first near-infrared scattered-light detection of the transitional disk around V1247 Ori, which was obtained using high-resolution polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging in the H band reveals the disk morphology at separations of ~0.14"-0.86" (54-330 au) from the central star. The polarized intensity (PI) image shows a remarkable arc-like structure toward the southeast of the star, whereas the fainter northwest region does not exhibit any notable features. The shape of the arm is consistent with an arc of 0.28" $\pm$ 0.09" in radius (108 au from the star), although the possibility of a spiral arm with a small pitch angle cannot be excluded. V1247 Ori features an exceptionally large azimuthal contrast in scattered, polarized light; the radial peak of the southeastern arc is about three times brighter than the northwestern disk measured at the same distance from the star. Combined with the previous indication of an inhomogeneous density distribution in the gap at $\lesssim$46 au, the notable asymmetry in the outer disk suggests the presence of unseen companions and/or planet-forming processes ongoing in the arc.Comment: 21 pages, 5 figures, accepted for publication in PAS

Extreme Asymmetry in the Polarized Disk of V1247 Orionis *

We present the first near-infrared scattered-light detection of the transitional disk around V1247 Ori, which was obtained using high-resolution polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging in the H band reveals the disk morphology at separations of 0.′′14–0.′′86 (54–330 au) from the central star. The polarized intensity (PI) image shows a remarkable arc-like structure toward the southeast of the star, whereas the fainter northwest region does not exhibit any notable features. The shape of the arm is consistent with an arc of 0.′′28 0.′′09 in radius (108 au from the star), although the possibility of a spiral arm with a small pitch angle cannot be excluded. V1247 Ori features an exceptionally large azimuthal contrast in scattered, polarized light; the radial peak of the southeastern arc is about three times brighter than the northwestern disk measured at the same distance from the star. Combined with the previous indication of an inhomogeneous density distribution in the gap at < 46 au, the notable asymmetry in the outer disk suggests the presence of unseen companions and/or planet-forming processes ongoing in the arc.This work is supported by MEXT KAKENHI Nos. 23103005. S.K. acknowledges support from an STFC Ernest Rutherford Fellowship (ST/J004030/1) and Marie Curie CIG grant (SH-06192)

Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides

Sulfides are promising candidates for environment-friendly and cost-effective thermoelectric materials. In this article, we review the recent progress in all-length-scale hierarchical architecturing for sulfides and chalcogenides, highlighting the key strategies used to enhance their thermoelectric performance. We primarily focus on TiS2-based layered sulfides, misfit layered sulfides, homologous chalcogenides, accordion-like layered Sn chalcogenides, and thermoelectric minerals. CS2 sulfurization is an appropriate method for preparing sulfide thermoelectric materials. At the atomic scale, the intercalation of guest atoms/layers into host crystal layers, crystal-structural evolution enabled by the homologous series, and low-energy atomic vibration effectively scatter phonons, resulting in a reduced lattice thermal conductivity. At the nanoscale, stacking faults further reduce the lattice thermal conductivity. At the microscale, the highly oriented microtexture allows high carrier mobility in the in-plane direction, leading to a high thermoelectric power factor

Jood, P. and Ohta, M. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides. Materials 2015, 8, 1124–1149

The authors wish to make the following corrections to this paper [1]. [...