arXiv subjects

Yang Sun

Publications and source records attributed to Yang Sun.

279 records · Page 16Linked to original sources

arXiv1999

Multi-Phonon $γ$-Vibrational Bands and the Triaxial Projected Shell Model

We present a fully quantum-mechanical, microscopic, unified treatment of ground-state band and multi-phonon $γ$-vibrational bands using shell model diagonalization with the triaxial projected shell model. The results agree very well with data on the g- and $γ$-band spectra in $^{156-170}$Er, as well as with recently measured $4^+$ 2-phonon $γ$-bandhead energies in $^{166}$Er and $^{168}$Er. Multi-phonon $γ$-excitation energies are predicted.

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arXiv1999

An SU(4) Approach of High-Temperature Superconductivity and Antiferromagnetism

We present an SU(4) model of high-$T_c$ superconductivity. One dynamical symmetry of this model corresponds to the previously proposed SO(5) model for unification of superconductivity and antiferromagnetism, but there are two additional dynamical symmetries: SO(4), associated with antiferromagnetic order and SU(2), associated with a D-wave pairing condensate. These provide a 3-phase microscopic model of high-$T_c$ superconductivity and permit a clear understanding of the role played by the SO(5) symmetry.

cond-mat.supr-con↗

arXiv1999

On the Backbending Mechanism of $^{48}$Cr

The mechanism of backbending in $^{48}$Cr is investigated in terms of the Projected Shell Model and the Generator Coordinate Method. It is shown that both methods are reasonable shell model truncation schemes. These two quite different quantum mechanical approaches lead to a similar conclusion that the backbending is due to a band crossing involving an excited band which is built on simultaneously broken neutron and proton pairs in the ``intruder'' subshell $f_{7/2}$. It is pointed out that this type of band crossing is usually known to cause the second backbending in rare-earth nuclei.

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arXiv1999

Theoretical Constraints for Observation of Superdeformed Bands in the Mass-60 Region

The lightest superdeformed nuclei of the mass-60 region are described using the Projected Shell Model. In contrast to the heaviest superdeformed nuclei where a coherent motion of nucleons often dominates the physics, it is found that alignment of $g_{9/2}$ proton and neutron pairs determines the high spin behavior for superdeformed rotational bands in this mass region. It is predicted that, due to the systematics of shell fillings along the even--even Zn isotopic chain, observation of a regular superdeformed yrast band sequence will be unlikely for certain nuclei in this mass region.

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arXiv1999

The SO(5) Theory as a Critical Dynamical Symmetry

We use generalized coherent states to analyze the SO(5) theory of high-temperature superconductivity and antiferromagnetism. We demonstrate that the SO(5) symmetry can be embedded in a larger algebra that allows it to be interpreted as a critical dynamical symmetry interpolating between antiferromagnetic and superconducting phases. This dynamical interpretation suggests that SO(5) defines a phase with the character of a spin-glass for a significant range of doping.

cond-mat.supr-con↗

arXiv1998

Single Particle and Collective Structure for Nuclei near Sn-132

A new Nilsson single-particle structure is proposed for neutron-rich nuclei near $^{132}$Sn. In general, a large reduction in spin-orbit interaction is required and the neutron $N = 82$ gap persists in the new set of parameters. The ground state deformations for several isotopic chains are studied with this set and compared with the results of the standard set and with measured ones. Collective bands in two even-even, neutron-rich nuclei are calculated using the Projected Shell Model with the new set of parameters and improved agreement with existing data is found.

nucl-th↗

arXiv1994

``Chaos" in Nuclear High Spin Spectroscopy

The Projected Shell Model with zero-, two- and four-quasiparticle configurations is used to investigate the level statistics, i.e. chaoticity, of high spin spectroscopy. The model can describe many high spin phenomena and with the present configuration space has sufficient number of levels for statistical analysis. It is found that the degree of chaoticity has a sensitive dependence on the classification of levels in question, and that it steadily increases with excitation energy and angular momentum.

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arXiv1994

Varied Signature Splitting Phenomena in Odd Proton Nuclei

Varied signature splitting phenomena in odd proton rare earth nuclei are investigated. Signature splitting as functions of $K$ and $j$ in the angular momentum projection theory is explicitly shown and compared with those of the particle rotor model. The observed deviations from these rules are due to the band mixings. The recently measured $^{169}$Ta high spin data are taken as a typical example where fruitful information about signature effects can be extracted. Six bands, two of which have not yet been observed, were calculated and discussed in detail in this paper. The experimentally unknown band head energies are given.

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arXiv1994

Anomalous Crossing Frequency in Odd Proton Nuclei

A generic explanation for the recently observed anomalous crossing frequencies in odd proton rare earth nuclei is given. As an example, the proton ${1\over 2} [541]$ band in $^{175}$Ta is discussed in detail by using the angular momentum projection theory. It is shown that the quadrupole pairing interaction is decisive in delaying the crossing point and the changes in crossing frequency along the isotope chain are due to the different neutron shell fillings.

nucl-th↗