Thermodynamic properties of tetrameric bond-alternating spin chains

Thermodynamic properties of a tetrameric bond-alternating Heisenberg spin chain with ferromagnetic-ferromagnetic-antiferromagnetic-antiferromagnetic exchange interactions are studied using the transfer-matrix renormalization group and compared to experimental measurements. The temperature dependence of the uniform susceptibility exhibits typical ferrimagnetic features. Both the uniform and staggered magnetic susceptibilities diverge in the limit $T\to 0$, indicating that the ground state has both ferromagnetic and antiferromagnetic long-range orders. A double-peak structure appears in the temperature dependence of the specific heat. Our numerical calculation gives a good account for the temperature and field dependence of the susceptibility, the magnetization, and the specific heat for Cu(3-Clpy)$_{2}$(N$_{3}$)$_{2}$ (3-Clpy=3-Chloroyridine).Comment: 8 pages, 12 figures; Replaced with final version accepted in Phys. Rev.

THz wave transmission within the metal film coated double-dielectric-slab waveguides and the tunable filter application

publisher: Elsevier articletitle: THz wave transmission within the metal film coated double-dielectric-slab waveguides and the tunable filter application journaltitle: Optics Communications articlelink: http://dx.doi.org/10.1016/j.optcom.2015.04.049 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved.publisher: Elsevier articletitle: THz wave transmission within the metal film coated double-dielectric-slab waveguides and the tunable filter application journaltitle: Optics Communications articlelink: http://dx.doi.org/10.1016/j.optcom.2015.04.049 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved

Metal plate for guiding terahertz surface plasmon-polaritons and its sensing applications

publisher: Elsevier articletitle: Metal plate for guiding terahertz surface plasmon-polaritons and its sensing applications journaltitle: Optics Communications articlelink: http://dx.doi.org/10.1016/j.optcom.2014.11.046 content_type: article copyright: Copyright © 2014 Elsevier B.V. All rights reserved.publisher: Elsevier articletitle: Metal plate for guiding terahertz surface plasmon-polaritons and its sensing applications journaltitle: Optics Communications articlelink: http://dx.doi.org/10.1016/j.optcom.2014.11.046 content_type: article copyright: Copyright © 2014 Elsevier B.V. All rights reserved

Positive solutions for Sturm-Liouville boundary value problems in a Banach space

We consider the existence of single and multiple positive solutions for a second-order Sturm-Liouville boundary value problem in a Banach space. The sufficient condition for the existence of positive solution is obtained by the fixed point theorem of strict set contraction operators in the frame of the ODE technique. Our results significantly extend and improve many known results including singular and nonsingular cases

First-principles study on the effective masses of zinc-blend-derived Cu_2Zn-IV-VI_4 (IV = Sn, Ge, Si and VI = S, Se)

The electron and hole effective masses of kesterite (KS) and stannite (ST) structured Cu_2Zn-IV-VI_4 (IV = Sn, Ge, Si and VI = S, Se) semiconductors are systematically studied using first-principles calculations. We find that the electron effective masses are almost isotropic, while strong anisotropy is observed for the hole effective mass. The electron effective masses are typically much smaller than the hole effective masses for all studied compounds. The ordering of the topmost three valence bands and the corresponding hole effective masses of the KS and ST structures are different due to the different sign of the crystal-field splitting. The electron and hole effective masses of Se-based compounds are significantly smaller compared to the corresponding S-based compounds. They also decrease as the atomic number of the group IV elements (Si, Ge, Sn) increases, but the decrease is less notable than that caused by the substitution of S by Se.Comment: 14 pages, 6 figures, 2 table