arXiv subjects
Publications and source records attributed to Takaaki Sogo.
A general theory for the condensation of strongly bound quartets in infinite nuclear matter is presented. Critical temperatures for symmetric and asymmetric nuclear matter are evaluated. A fully nonlinear theory for the quartet order parameter, based on an analogy of the Gorkov approach to pairing, is presented and solved. The strong qualitative difference with pairing is pointed out.
The critical temperature for $α$-particle condensation in nuclear matter with Fermi surface imbalance between protons and neutrons is determined. The in-medium four-body Schrödinger equation, generalizing the Thouless criterion of the BCS transition, is applied using a Hartree-Fock wave function for the quartet projected onto zero total momentum in matter with different chemical potentials for protons and neutrons.
The theory for condensation of higher fermionic clusters is developed. Fully selfconsistent nonlinear equations for the quartet order parameter in strongly coupled fermionic systems are established and solved. The breakdown of the quasiparticle picture is pointed out. Derivation of numerically tractable approximation is described. The momentum projected factorisation ansatz of Ref. \cite{slr09} for the order parameter is employed again. As a definite example the condensation of $α$ particles in nuclear matter is worked out.
We consider a uniform dipolar Fermi gas in two-dimensions (2D) where the dipole moments of fermions are aligned by an orientable external field. We obtain the ground state of the gas in Hartree-Fock approximation and investigate RPA stability against density fluctuations of finite momentum. It is shown that the density wave instability takes place in a broad region where the system is stable against collapse. We also find that the critical temperature can be a significant fraction of Fermi temperature for a realistic system of polar molecules.
We consider a system of quantum degenerate spin polarized fermions in a harmonic trap at zero temperature, interacting via dipole-dipole forces. We introduce a variational Wigner function to describe the deformation and compression of the Fermi gas in phase space and use it to examine the stability of the system. We emphasize the important roles played by the Fock exchange term of the dipolar interaction which results in a non-spherical Fermi surface.