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La-doped ASnO3 (A = Ba, Sr) have great potential as advanced transparent oxide semiconductors due to their large optical bandgap and relatively high electron mobility. The bandgap of Ba1-xSrxSnO3 solid solution increases from 3.2 eV (BaSnO3) to 4.6 eV (SrSnO3) with x. However, the increase in the bandgap is accompanied by reductions in the electrical conductivity. The versatility in the changes in the electrical properties are not trivial, and the property optimization has been challenging. Here we propose a simple metric for quantifying the transport properties of ASnO3. We investigated the electron/thermal transport properties of Ba1-xSrxSnO3 solid solution films and their relationship with the lattice distortion. The results suggest that the all transport properties of Ba1-xSrxSnO3 are dominated by the lattice distortion. This phenomenon is attributed to the distortions in the SnO6 octahedron, which consists the conduction band.

To discuss a possible observation of large-amplitude nuclear shape mixing by nuclear reaction, we employ a simple collective model and evaluate transition densities, with which the differential cross sections are obtained through the microscopic coupled-channel calculation. Assuming the spherical-to-prolate shape transition, we focus on large-amplitude shape mixing associated with the softness of the collective potential in the $\beta$ direction. We introduce a simple model based on the five-dimensional quadrupole collective Hamiltonian, which simulates a chain of isotopes that exhibit spherical-to-prolate shape phase transition. Taking $^{154}$Sm as an example and controlling the model parameters, we study how the large-amplitude shape mixing affects the elastic and inelastic proton scatterings. The calculated results suggest that the inelastic cross section of the $2_2^+$ state tells us an important role of the quadrupole shape mixing., Comment: 10 pages, 7 figures

We propose a new set of equations to determine the collective Hamiltonian including the second-order collective-coordinate operator on the basis of the adiabatic self-consistent collective-coordinate (ASCC) theory. We illustrate, with the two-level Lipkin model, that the collective operators including the second-order one are self-consistently determined. We compare the results of the calculations with and without the second-order operator and show that, without the second-order operator, the agreement with the exact solution becomes worse as the excitation energy increases, but that, with the second-order operator included, the exact solution is well reproduced even for highly excited states. We also reconsider which equations one should adopt as the basic equations in the case where only the first-order operator is taken into account, and suggest an alternative set of fundamental equations instead of the conventional ASCC equations. Moreover, we briefly discuss the gauge symmetry of the new basic equations we propose in this paper., Comment: 30 pages, 11 figures

We investigate the relation of $a^\dagger a$ terms in the collective operator to the higher-order terms in the adiabatic self-consistent collective coordinate (ASCC) method. In the ASCC method, a state vector is written as $e^{i\hat G(q,p,n)}|\phi(q)\rangle$ with $\hat G(q,p,n)$ which is a function of collective coordinate $q$, its conjugate momentum $p$ and the particle number $n$. According to the generalized Thouless theorem, $\hat G$ can be written as a linear combination of two-quasiparticle creation and annihilation operators $a^\dagger_\mu a^\dagger_\nu$ and $a_\nu a_\mu$. We show that, if $a^\dagger a$ terms are included in $\hat G(q,p,n)$, it corresponds to the higher-order terms in the adiabatic expansion of $\hat G$. This relation serves as a prescription to determine the higher-order collective operators from the $a^\dagger a$ part of the collective operator, once it is given without solving the higher-order equations of motion., Comment: 19 pages, no figure

Effects of the isospin-symmetry breaking (ISB) beyond mean-field Coulomb terms are systematically studied in nuclear masses near the $N=Z$ line. The Coulomb exchange contributions are calculated exactly. We use extended Skyrme energy density functionals (EDFs) with proton-neutron-mixed densities, to which we add new terms breaking the isospin symmetry. Two parameters associated with the new terms are determined by fitting mirror and triplet displacement energies (MDEs and TDEs) of isospin multiplets. The new EDFs reproduce MDEs for the $T=\frac12$ doublets and $T=1$ triplets, and TDEs for the $T=1$ triplets. Relative strengths of the obtained isospin-symmetry-breaking terms {\em are not} consistent with the differences in the $NN$ scattering lengths, $a_{nn}$, $a_{pp}$, and $a_{np}$. Based on low-energy experimental data, it seems thus impossible to delineate the strong-force ISB effects from beyond-mean-field Coulomb-energy corrections., Comment: Letter 20 pages, 4 figures, Supplemental Material 11 pages, 6 figures; important bug corrected & conclusions modified; submitted to Physics Letters B

We study gauge symmetry breaking by adiabatic approximation in the adiabatic self-consistent collective coordinate (ASCC) method. In the previous study, we found that the gauge symmetry of the equation of collective submanifold is (partially) broken by its decomposition into the three moving-frame equations depending on the order of $p$. In this study, we discuss the gauge symmetry breaking by the truncation of the adiabatic expansion. A particular emphasis is placed on the symmetry under the gauge transformations which are not point transformations. We also discuss a possible version of the ASCC method including the higher-order operators which can keep the gauge symmetry., Comment: 26 pages, no figure

Isospin-symmetry-violating class II and III contact terms are introduced into the Skyrme energy density functional to account for charge dependence of the strong nuclear interaction. The two new coupling constants are adjusted to available experimental data on triplet and mirror displacement energies, respectively. We present preliminary results of the fit, focusing on its numerical stability with respect to the basis size., Comment: talk presented at the Zakopane Conference on Nuclear Physics, Zakopane, Poland, August 28 - September 4, 2016

We discuss the nature of the low-frequency quadrupole vibrations from small-amplitude to large-amplitude regimes. We consider full five-dimensional quadrupole dynamics including three-dimensional rotations restoring the broken symmetries as well as axially symmetric and asymmetric shape fluctuations. Assuming that the time-evolution of the self-consistent mean field is determined by five pairs of collective coordinates and collective momenta, we microscopically derive the collective Hamiltonian of Bohr and Mottelson, which describes low-frequency quadrupole dynamics. We show that the five-dimensional collective Schr\"odinger equation is capable of describing large-amplitude quadrupole shape dynamics seen as shape coexistence/mixing phenomena. We summarize the modern concepts of microscopic theory of large-amplitude collective motion, which is underlying the microscopic derivation of the Bohr-Mottelson collective Hamiltonian., Comment: 62 pages, 6 figures, Review article, Invited Comment in Focus Issue of Physica Scripta to celebrate the 40-year anniversary of the 1975 Nobel Prize to A. Bohr, B. R. Mottelson and L. J. Rainwater (Phys. Scr. 91 (2016) 063014). arXiv admin note: text overlap with arXiv:1606.04717

The adiabatic self-consistent collective coordinate (ASCC) method is a practical method for the description of large-amplitude collective motion in atomic nuclei with superfluidity and an advanced version of the adiabatic time-dependent Hartree-Fock-Bogoliubov theory. We investigate the gauge symmetry in the ASCC method on the basis of the theory of constrained systems. The gauge symmetry in the ASCC method is originated from the constraint on the particle number in the collective Hamiltonian, and it is partially broken by the adiabatic expansion. The validity of the adiabatic expansion under the general gauge transformation is also discussed., Comment: 20 pages. Accepted for publication in Prog. Theor. Exp. Phys

Assuming that the time-evolution of the self-consistent mean field is determined by five pairs of collective coordinate and collective momentum, we microscopically derive the collective Hamiltonian for low-frequency quadrupole modes of excitation. We show that the five-dimensional collective Schr\"odinger equation is capable of describing large-amplitude quadrupole shape dynamics seen as shape coexistence/mixing phenomena. We focus on basic ideas and recent advances of the approaches based on the time-dependent mean-field theory, but relations to other time-independent approaches are also briefly discussed., Comment: 24 pages, 4 figures. Contribution to the Focus Issue of Journal of Physics G on "Shape Coexistence in Atomic Nuclei" edited by John Wood and Kris Heyde

We report comprehensive studies of the crystallographic,magnetic, and thermal properties of a spinel-type magnetically frustrated compound, CoAl2O4, and a magnetically diluted system,Co1-xZnxAl2O4. These studies revealed the effects of dilution and disorder when the tetrahedral magnetic Co ion was replaced by the nonmagnetic Zn ion. Low-temperature anomalies were observed in magnetic susceptibility at x < 0.6. A multicritical point was apparent at T = 3.4 K and x = 0.12, where the antiferromagnetic, spin glass-like, and paramagnetic phases met. At that point, the quenched ferromagnetic component induced by a magnetic field during cooling was sharply enhanced and was observable below x = 0.6. Around x = 0.6, magnetic susceptibility and specific heat were described by temperature power laws, chi ~ C/T ~ T-d, in accord with the site percolation threshold of the diamond lattice. This behavior is reminiscent of a quantum critical singularity. We propose an x-temperature phase diagram in the range 0 < x < 1 for Co1-xZnxAl2O4. The transition temperature of CoAl2O4 determined from magnetic susceptibility measured under hydrostatic pressure increased with increasing pressure., Comment: 30 pages, 12 figures

We have performed calculations based on the Skyrme energy density functional (EDF) that includes arbitrary mixing between protons and neutrons. In this framework, single-particle states are generalized as mixtures of proton and neutron components. The model assumes that the Skyrme EDF is invariant under the rotation in isospin space and the Coulomb force is the only source of the isospin symmetry breaking. To control the isospin of the system, we employ the isocranking method, which is analogous to the standard cranking approach used for describing high-spin states. Here, we present results of the isocranking calculations performed for the isobaric analog states in $A = 40$ and $A = 54$ nuclei., Comment: 6 pages, 7 figures, talk given at the 2nd Conference on "Advances in Radioactive Isotope Science 2014" (ARIS 2014), Tokyo, Japan, Jun. 1-6, 2014