Structure and stability of quasi-two-dimensional boson–fermion mixtures with vortex–antivortex superposed states

Abstract

We investigate the equilibrium properties of a quasi-two-dimensional degenerate boson-fermion mixture (DBFM) with a bosonic vortex-antivortex superposed state (VAVSS) using a quantumhydrodynamic model. We show that, depending on the choice of parameters, the DBFM with a VAVSS can exhibit rich phase structures. For repulsive boson-fermion (BF) interaction, the Bose-Einstein condensate (BEC) may constitute a petal-shaped "core" inside the honeycomb-like fermionic component, or a ring-shaped joint "shell" around the onion-like fermionic cloud, or multiple segregated "islands" embedded in the disc-shaped Fermi gas. For attractive BF interaction just below the threshold for collapse, an almost complete mixing between the bosonic and fermionic components is formed, where the fermionic component tends to mimic a bosonic VAVSS. The influence of an anharmonic trap on the density distributions of the DBFM with a bosonic VAVSS is discussed. In addition, a stability region for different cases of DBFM (without vortex, with a bosonic vortex, and with a bosonic VAVSS) with specific parameters is given.

Structure and dynamics of a rotating superfluid Bose-Fermi mixture

“…2(b1) and 2(b2)], which is usually referred as demixing. The similar mixing-demixing transition phenomenon has also been found in the studies of degenerate boson-fermion mixtures [35][36][37][38][39] or two-component BECs [33,[40][41][42][43]. Finally, region IV marks an inlaid separated phase in which the fermionic superfluid is divided into two segments and inlaid into the outskirts of the BEC [Figs.…”

“…The ground-state structures of SBFMs are different from those of degenerate boson-fermion mixtures [35][36][37][38][39]. In the latter case, there is no s-wave interaction between identical fermions in the spin-polarized state due to the Pauli exclusion principle.…”

“…In the latter case, there is no s-wave interaction between identical fermions in the spin-polarized state due to the Pauli exclusion principle. Depending on the BB and BF interactions, the density profile of a degenerate boson-fermion mixture may display a core-shell-shaped separated phase, where the Fermi gas forms a shell around or a core inside the BEC, or even both [35][36][37][38][39]. However, our simulation shows that in a wide range of parameter values, the SBFM supports neither a separated phase of fermions constituting a shell around the BEC nor a staggered separated phase of fermions becoming both a shell around and a core inside the BEC (see Figs.…”

Structure of two-component Bose-Einstein condensates with respective vortex-antivortex superposition states

“…On the other hand, the equilibrium properties of the present system are also evidently different from those of DBFM with a bosonic VAVSS [29]. In the latter case, due to the Pauli exclusion principle, there is no s-wave interaction between identical fermions in the spin polarized state.…”

“…In this paper, length, time, energy, and angular momentum are in units of d 0 = /2mω ⊥ , 1/ω ⊥ , ω ⊥ , and , respectively. g 1 , g 2 ,and g denote dimensionless intra-and intercomponent coupling strengths which are proportional to the corresponding s-wave scattering lengths a j , a ij (j = 1, 2) between intra-and intercomponent atoms and the atom numbers N 1,2 in species 1 and 2 [1,2,28,29]. The two wave functions are normalized as |ψ 1,2 | 2 rdrdθ = 1.…”