arXiv subjects

J. Usukura

Publications and source records attributed to J. Usukura.

4 recordsLinked to original sources

arXiv2000

Properties of few-electron artificial atoms

The spectra of quantum dots of different geometry (``quantum ring'', ``quantum cylinder'', ``spherical square-well'' and ``parabolic confinement'') are studied. The stochastic variational method on correlated Gaussian basis functions and a large scale shell-model approach have been used to investigate these ``artificial'' atoms and their properties in magnetic field. Accurate numerical results are presented for $N$=2-8 electron systems.

cond-mat.mes-hall↗

arXiv1998

Signature of the existence of the positronium molecule

The positronium molecule (Ps$_2$) has not been experimentally observed yet because its tiny (4.5 eV) binding energy cannot be detected when the molecule annihilates by emitting two photons with energy of 0.51 MeV each. It is shown in this paper that the electric dipole transition between the recently found L=1 excited-state and the L=0 ground-state with its characteristic photon energy of 4.94 eV is a clear signature of the existence of the positronium molecule and the possibility of its experimental observation is realistic. The probability of this transition is about 17 % of the total decay rate. An other Coulomb four-body system containing positron, HPs (the positronium hydride or hydrogen positride), is also included for comparison.

physics.atom-ph↗

arXiv1998

Second bound state of the positronium molecule and biexcitons

A new, hitherto unknown bound state of the positronium molecule, with orbital angular momentum L=1 and negative parity is reported. This state is stable against autodissociation even if the masses of the positive and negative charges are not equal. The existence of a similar state in two-dimension has also been investigated. The fact that the biexcitons have a second bound state may help the better understanding of their binding mechanism.

cond-mat.mes-hall↗

arXiv1997

New representation of orbital motion with arbitrary angular momenta

A new formulation is presented for a variational calculation of $N$-body systems on a correlated Gaussian basis with arbitrary angular momenta. The rotational motion of the system is described with a single spherical harmonic of the total angular momentum $L$, and thereby needs no explicit coupling of partial waves between particles. A simple generating function for the correlated Gaussian is exploited to derive the matrix elements. The formulation is applied to various Coulomb three-body systems such as $e^-e^-e^+, ttμ, tdμ$, and $αe^-e^-$ up to $L=4$ in order to show its usefulness and versatility. A stochastic selection of the basis functions gives good results for various angular momentum states.

nucl-th↗