arXiv subjects

Naotaka Yoshinaga

Publications and source records attributed to Naotaka Yoshinaga.

6 recordsLinked to original sources

arXiv2026

Spherical-tensor description of the Jahn--Teller--Hubbard molecule and local electron--phonon entanglement

We investigate the localized-electron character of the Mott-insulating phase in A$_3$C$_{60}$ using a single-site multiorbital electron model coupled to anisotropic molecular vibrations (Jahn--Teller phonons). We apply the spherical-tensor formalism, a framework originally developed in nuclear physics, to analyze the electron--phonon-coupled ground-state multiplet. Focusing on multipole moments, we find that both the conventional electronic quadrupole moment and the lattice displacement associated with the molecular vibrations vanish, even though the degenerate ground-state multiplet implies the presence of quadrupolar degrees of freedom. By analyzing these degrees of freedom within the spherical-tensor framework, we introduce composite (two-body) quadrupole operators involving both electrons and phonons and study their parameter dependence numerically. Furthermore, using quasispin selection rules, we demonstrate that the composite quadrupole does not couple to either the conventional quadrupole or lattice-displacement operators, thereby distinguishing it fundamentally from standard quadrupolar degrees of freedom. In addition, we investigate the nature of the electron--phonon entanglement and characterize it from the viewpoint of angular momentum. Analysis of the entanglement spectrum reveals that the ground state consists of superpositions of multi-phonon states with angular momenta $L_{\rm ph}=2$ and $L_{\rm ph}=3$, formed through coupling to three-electron states with $L=1$ and $L=2$.

cond-mat.str-el↗

arXiv2019

Electric dipole moment of $^{199}$Hg atom from P, CP-odd electron-nucleon interaction

We calculate the effect of the P, CP-odd electron-nucleon interaction on the electric dipole moment of the $^{199}$Hg atom by evaluating the nuclear spin matrix elements in terms of the nuclear shell model. It is found that the neutron spin matrix element of the $^{199}$Hg nucleus is $\langle Ψ|\, σ_{nz} | Ψ\rangle \approx -0.4$ with a dominant configuration of $p_{1/2}$ orbital neutron. We also derive constraints on the CP phases of Higgs-doublet models, supersymmetric models, and leptoquark models from the latest experimental limit $|d_{\rm Hg}| < 7.4 \times 10^{-30}e$ cm.

nucl-th↗

arXiv2018

Spin polarized phases in strongly interacting matter: interplay between axial-vector and tensor mean fields

The spontaneous spin polarization of strongly interacting matter due to axial-vector and tensor type interactions is studied at zero temperature and high baryon-number densities. We start with the mean-field Lagrangian for the axial-vector and tensor interaction channels, and find in the chiral limit that the spin polarization due to the tensor mean field ($U$) takes place first as the density increases for sufficiently strong coupling constants, and then that due to the axial-vector mean field ($A$) emerges in the region of finite tensor mean field. This can be understood that making the axial-vector mean field finite requires a broken chiral symmetry somehow, which is achieved by the finite tensor mean field in the present case. It is also found from symmetry argument that there appear the type I (II) Nambu-Goldstone modes with a linear (quadratic) dispersion in the spin polarized phase with $U\neq0$ and $A=0$ ($U\neq0$ and $A\neq0$), although these two phases exhibit the same symmetry breaking pattern.

hep-ph↗

arXiv2005

Molecular dynamics simulation for baryon-quark phase transition at finite temperature and density

We study the baryon-quark phase transition in a molecular dynamics (MD) of quark degrees of freedom at finite temperature and density. The baryon state at low density and temperature, and the deconfined quark state at high density and temperature are reproduced. We investigate the equations of state of matters with different $u$-$d$-$s$ compositions. Then we draw phase diagrams in the temperature-density plane by this simulation. It is found that the baryon-quark transition is sensitive to the quark width.

nucl-th↗

arXiv2004

Stability and structure of quark matter in a molecular dynamics framework

We study stability and structure of quark matters as a function of density in a framework of molecular dynamics (MD). Using appropriate effective interactions and the frictional cooling method, we search for the minimum energy of the system. Transition from confined to deconfined phase is observed at densities of 2 -- 3$ρ_0$, where $ρ_0$ is the nuclear matter saturation density. The $uds$ matter becomes more stable than the charge-neutral $ud$ matter at 3$ρ_0$, but the $udd$ matter is the most stable even at high density.

nucl-th↗

arXiv1995

Nuclear Mass Dependence of Chaotic Dynamics in Ginocchio Model

The chaotic dynamics in nuclear collective motion is studied in the framework of a schematic shell model which has only monopole and quadrupole degrees of freedom. The model is shown to reproduce the experimentally observed global trend toward less chaotic motion in heavier nuclei. The relation between current approach and the earlier studies with bosonic models is discussed.

nucl-th↗