Reply to ``Comment on `Inverse exciton series in the optical decay of an excitonic molecule' "

As a reply to the Comment by I.S. Gorban {\it et al.} (Phys. Rev. B, preceding paper) we summarize our criticism on their claim of the first observation of the $M$ series in $\beta$-ZnP$_2$. We support our analysis by reporting the first observation of inverse {\it polariton} series from the excitonic molecules selectively generated at ${\bf K}_m \simeq {\bf 0}$ in a CuCl single crystal. This observation and its explanation within the bipolariton model complete our proof of the biexcitonic origin of the inverse series.Comment: The Comment by I.S. Gorban et al. has been rejecte

Soft and Hard Magnetic Properties of Nanocrystalline Fe-M-B (M=Zr, Nd) Base Alloys Containing Intergranular Amorphous Phase

This paper reviews our recent results of the soft and hard magnetic properties of nanocrystalline Fe-rich Fe-M-B (M=Nd or Zr) base alloys containing an intergranular amorphous phase. Based on the previous results that the soft magnetic alloys in Fe-Si-B-Nb-Cu and Fe-Zr-B systems do not have zero magnetostriction (λ_s), the effect of the additional Al or Si on the λ_s and magnetic properties was examined for the nanocrystalline Fe-Zr-B-Al and Fe-Zr-B-Si alloys. The soft magnetic properties of high Bs above 1.5 T and high μ_e above 1.5x10^4 combined with zero λ_s were obtained for the Fe_Zr_7B_3Al_2 and Fe_Zr_7B_3Si_4 alloys annealed for 3.6 ks in the annealing temperature (Ta) range of 823 to 923 K. This is in contrast to the previous result that the good soft magnetic properties of the nanocrystalline Fe_Zr_7B_3 alloy are obtained in the narrow Ta range around 923 K. The remarkable extension of the Ta range seems to be attributed to the zero λ_s. The replacement of Zr by Nd in the Fe_M_7B_3 alloys was found to cause rather good hard magnetic properties of 1.3 T for Br. 260 kA/m for iHc and 146 kJ/m^3 for (BH)_ in a triplex nanostructure of bcc-Fe with a size of 20 nm, tetragonal Fe_Nd_2B with a size of 15 nm and intergranular amorphous phase with a thickness of 5 to 10 nm. The hard magnetic properties are obtained for the nanostructure containing 80 % soft magnetic phases and 20 % Fe_Nd_2B in volume. The notable result is presumably due to the effective action of the intergranular amorphous network phase which can act as a resistance against the nucleation of the reversion of magnetic domain walls leading to the increase in iHc as well as an exchange magnetic coupling medium between bcc-Fe and bcc-Fe or tetragonal Fe_Nd_2B phases leading to the high Br. This presumption is also supported from the result that no good hard magnetic properties are obtained for the over annealed sample without intergranular amorphous phase as well as for the use of the sample which does not consist of a mostly single amorphous phase in the as-quenched state. Thus, the soft and hard magnetic properties for the Fe-M-B alloys are obtained only in the optimal nanostructures. The fabrication of a new nanostructure is expected to cause the appearance of other function properties even at compositions where no useful properties have not been obtained

Scaling in the correlation energies of two-dimensional artificial atoms

We find an unexpected scaling in the correlation energy of artificial atoms, i.e., harmonically confined two-dimensional quantum dots. The scaling relation is found through extensive numerical examinations including Hartree-Fock, variational quantum Monte Carlo, density-functional, and full configuration-interaction calculations. We show that the correlation energy, i.e., the true ground-state total energy subtracted by the Hartree-Fock total energy, follows a simple function of the Coulomb energy, confimenent strength and, the number of electrons. We find an analytic expression for this function, as well as for the correlation energy per particle and for the ratio between the correlation and total energies. Our tests for independent diffusion Monte Carlo and coupled-cluster results for quantum dots -- including open-shell data -- confirm the generality of the obtained scaling. As the scaling is also well applicable to $\gtrsim$ 100 electrons, our results give interesting prospects for the development of correlation functionals within density-functional theory.Comment: Accepted to Journal of Physics: Condensed Matte

Study on Photon Activation Analysis of Carbon in Glasses for Fiber Amplifiers by Using the Flow Method for the Rapid Separation of ^<11>C(II. Radiochemistry)

We have studied nuclear interference from a matrix produced by (γ, n), (γ, 2n), (γ, p) and (n, γ) reactions and a flow method for ^C separation in order to develop an approach for the photon activation analysis of carbon in InF_3-based fluoride, chalcogenide and tellurite glasses for fiber amplifiers. We found that seventeen radionuclides are produced from these glasses and chemical separation is necessary to determine carbon. For the flow method, which involves the fusion of an irradiated sample with an oxidizer, the conversion of ^C into ^CO_2, and the absorption of ^C in ethanolamine solution, we used a mixture of Pb_3O_4 and B_2O_3 as the oxidizer. We also found that the reaction between ^F(γ, n) and ^Na(γ, αn) in the ethanolamine solution produced ^F contamination with fluoride and chalcogenide glasses and that this flow method can only be applied to tellurite glasses. We confirmed that the chemical yield of the flow method was close to 100 % when determining carbon in standard steel samples by using lithium carbonate as a standard sample. We determined that the carbon concentrations in two kinds of tellurite glass were 8 to 13 and 21 to 28 ppm, respectively

High Permeability and Low Core Losses of Nanocrystalline Fe-Nb-Zr-B-Cu Alloys

Nanocrystalline Fe-M-B (M=Zr or Nb) alloys prepared by crystallization of rapidly quenched amorphous ribbons are known as a new class of soft magnets with high saturation magnetization. In order to improve their soft magnetic properties further, the reduction of their magnetostriction to zero was attempted by a combined addition of Zr and Nb, because the signs of the magnetostriction of the Fe-Zr-B and the Fe-Nb-B at each optimum condition are known to be opposite. Further, the B concentration was reinvestigated under a Cu addition and the combined addition of Zr and Nb in order to further refine the grain size and to improve the intergranular exchange coupling. As a result, the small average grain size of 8nm and nearly zero magnetostriction has been simultaneously obtained in the Fe_Nb_Zr_B_8Cu_1 alloy. This alloy simultaneously exhibits the high permeability of 100, 000 (at 1kHz) and the high saturation flux density of 1.53T, satisfying the both properties in the highest level among the rapidly quenched ribbons ever reported. The core losses of the nanocrystalline Fe_Nb_Zr_B_8Cu_1 alloy are lower than those of the amorphous Fe-Si-B alloys over a wide frequency and Bm (maximum induction) range. Further, the core losses are almost unchanged under the stresses such as epoxy resin molding. These new nanocrystalline materials are suitable for use in advanced electronic devices such as inductors or transformers

Mechanism, dynamics, and biological existence of multistability in a large class of bursting neurons

Multistability, the coexistence of multiple attractors in a dynamical system, is explored in bursting nerve cells. A modeling study is performed to show that a large class of bursting systems, as defined by a shared topology when represented as dynamical systems, is inherently suited to support multistability. We derive the bifurcation structure and parametric trends leading to multistability in these systems. Evidence for the existence of multirhythmic behavior in neurons of the aquatic mollusc Aplysia californica that is consistent with our proposed mechanism is presented. Although these experimental results are preliminary, they indicate that single neurons may be capable of dynamically storing information for longer time scales than typically attributed to nonsynaptic mechanisms.Comment: 24 pages, 8 figure