7,402 research outputs found

    Neutrinoless double-beta decay matrix elements in large shell-model spaces with the generator-coordinate method

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    We use the generator-coordinate method with realistic shell-model interactions to closely approximate full shell-model calculations of the matrix elements for the neutrinoless double-beta decay of 48^{48}Ca, 76^{76}Ge, and 82^{82}Se. We work in one major shell for the first isotope, in the f5/2pg9/2f_{5/2}pg_{9/2} space for the second and third, and finally in two major shells for all three. Our coordinates include not only the usual axial deformation parameter β\beta, but also the triaxiality angle γ\gamma and neutron-proton pairing amplitudes. In the smaller model spaces our matrix elements agree well with those of full shell-model diagonalization, suggesting that our Hamiltonian-based GCM captures most of the important valence-space correlations. In two major shells, where exact diagonalization is not currently possible, our matrix elements are only slightly different from those in a single shell.Comment: 8 pages, 7 figure

    Searching for high-KK isomers in the proton-rich A80A\sim80 mass region

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    Configuration-constrained potential-energy-surface calculations have been performed to investigate the KK isomerism in the proton-rich A80A\sim80 mass region. An abundance of high-KK states are predicted. These high-KK states arise from two and four-quasi-particle excitations, with Kπ=8+K^{\pi}=8^{+} and Kπ=16+K^{\pi}=16^{+}, respectively. Their excitation energies are comparatively low, making them good candidates for long-lived isomers. Since most nuclei under studies are prolate spheroids in their ground states, the oblate shapes of the predicted high-KK states may indicate a combination of KK isomerism and shape isomerism

    Normal heat conduction in one dimensional momentum conserving lattices with asymmetric interactions

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    The heat conduction behavior of one dimensional momentum conserving lattice systems with asymmetric interparticle interactions is numerically investigated. It is found that with certain degree of interaction asymmetry, the heat conductivity measured in nonequilibrium stationary states converges in the thermodynamical limit, in clear contrast to the well accepted viewpoint that Fourier's law is generally violated in low dimensional momentum conserving systems. It suggests in nonequilibrium stationary states the mass gradient resulted from the asymmetric interactions may provide an additional phonon scattering mechanism other than that due to the nonlinear interactions.Comment: 4 pages, 4 figure

    The upper critical field and its anisotropy in LiFeAs

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    The upper critical field μ0Hc2(Tc)\mu_0H_{c2}(T_c) of LiFeAs single crystals has been determined by measuring the electrical resistivity using the facilities of pulsed magnetic field at Los Alamos. We found that μ0Hc2(Tc)\mu_0H_{c2}(T_c) of LiFeAs shows a moderate anisotropy among the layered iron-based superconductors; its anisotropic parameter γ\gamma monotonically decreases with decreasing temperature and approaches γ1.5\gamma\simeq 1.5 as T0T\rightarrow 0. The upper critical field reaches 15T (HcH\parallel c) and 24.2T (HabH\parallel ab) at T=T=1.4K, which value is much smaller than other iron-based high TcT_c superconductors. The temperature dependence of μ0Hc2(Tc)\mu_0H_{c2}(T_c) can be described by the Werthamer-Helfand-Hohenberg (WHH) method, showing orbitally and (likely) spin-paramagnetically limited upper critical field for HcH\parallel c and HabH\parallel ab, respectively.Comment: 5 pages,5 figure

    Reduced dynamics with renormalization in solid-state charge qubit measurement

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    Quantum measurement will inevitably cause backaction on the measured system, resulting in the well known dephasing and relaxation. In this report, in the context of solid--state qubit measurement by a mesoscopic detector, we show that an alternative backaction known as renormalization is important under some circumstances. This effect is largely overlooked in the theory of quantum measurement.Comment: 12 pages, 4 figure