5,241 research outputs found
Antiferromagnetic and structural transitions in the superoxide KO2 from first principles: A 2p-electron system with spin-orbital-lattice coupling
KO2 exhibits concomitant antiferromagnetic (AFM) and structural transitions,
both of which originate from the open-shell 2p electrons of O
molecules. The structural transition is accompanied by the coherent tilting of
O molecular axes. The interplay among the spin-orbital-lattice
degrees of freedom in KO2 is investigated by employing the first-principles
electronic structure theory and the kinetic-exchange interaction scheme. We
have shown that the insulating nature of the high symmetry phase of KO2 at high
temperature (T) arises from the combined effect of the spin-orbit coupling and
the strong Coulomb correlation of O 2p electrons. In contrast, for the low
symmetry phase of KO2 at low T with the tilted O molecular axes, the
band gap and the orbital ordering are driven by the combined effects of the
crystal-field and the strong Coulomb correlation. We have verified that the
emergence of the O 2p ferro-orbital ordering is essential to achieve the
observed AFM structure for KO2
Correlated Electronic Structures and the Phase Diagram of Hydrocarbon-based Superconductors
We have investigated correlated electronic structures and the phase diagram of electron-doped hydrocarbon molecular solids, based on the dynamical mean-field theory. We have found that the ground state of hydrocarbon-based superconductors such as electron-doped picene and coronene is a multi-band Fermi liquid, while that of non-superconducting electron-doped pentacene is a single-band Fermi liquid in the proximity of the metal-insulator transition. The size of the molecular orbital energy level splitting plays a key role in producing the superconductivity of electron-doped hydrocarbon solids. The multi-band nature of hydrocarbon solids would boost the superconductivity through the enhanced density of states at the Fermi level.X11910sciescopu
Two-dimensional charge distributions of the baryon: Interpolation between the nonrelativistic and ultrarelativistic limit
We investigate how the charge distributions of both the unpolarized and
transversely polarized baryon change as the longitudinal
momentum~() of the baryon increases from to
in a Wigner phase-space perspective. When the baryon is
longitudinally polarized, its two-dimensional charge distribution is kept to be
spherically symmetric with varied, whereas when the baryon is
transversely polarized along the -axis, the quadrupole contribution emerges
at the rest frame (). When grows, the electric dipole and
octupole moments are induced. The induced dipole moment dominates over other
higher multipole contributions and governs the deformation of the charge
distribution of the baryon.Comment: 22 pages, 12 figure
Instanton effects on electromagnetic transitions of charmonia
We investigate the mass spectrum and electromagnetic transitions of
charmonia, emphasizing the instanton effects on them. The heavy-quark potential
consists of the Coulomb-like potential from one-gluon exchange and the linear
confining potential. We introduce the nonperturbative heavy-quark potential
derived from the instanton vacuum. We also consider the screened confining
potential, which better describes the electromagnetic decays of higher excited
states. Using this improved heavy-quark potential, we compute the mass spectrum
and electromagnetic decays of the charmonia. Focusing on the instanton effects,
we discuss the results compared with the experimental data and those from other
works. The instanton effects are marginal on the electromagnetic decays of
charmonia.Comment: 10 pages and 4 figures. The final version to be published in Progress
of Theoretical and Experimental Physic
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