Some ground-state properties of a binary boson mixture

MANFRED L. RISTIG, Stefano Fantoni, K. E. K�rten

Vittorio Penna, Alessandra Contestabile, Andrea Richaud

We investigated the spatial phase separation of the two components forming a bosonic mixture distributed in a four-well lattice with a ring geometry. We studied the ground state of this system, described by means of a binary Bose–Hubbard Hamiltonian, by implementing a well-known coherent-state picture which allowed us to find the semi-classical equations determining the distribution of boson components in the ring lattice. Their fully analytic solutions, in the limit of large boson numbers, provide the boson populations at each well as a function of the interspecies interaction and of other significant model parameters, while allowing to reconstruct the non-trivial architecture of the ground-state four-well phase diagram. The comparison with the L-well (L=2,3) phase diagrams highlights how increasing the number of wells considerably modifies the phase diagram structure and the transition mechanism from the full-mixing to the full-demixing phase controlled by the interspecies interaction. Despite the fact that the phase diagrams for L=2,3,4 share various general properties, we show that, unlike attractive binary mixtures, repulsive mixtures do not feature a transition mechanism which can be extended to an arbitrary lattice of size L.

K. E. Kürten, MANFRED L. RISTIG

Tapash Chakraborty

We present a general formalism for the ground state of binary boson mixtures where the Jastrow-type ground-state wave function is optimized by solving the Euler-Lagrange equations in the hypernetted-chain scheme. This method is expected to provide more accurate information for the binary boson systems compared to the methods currently available. For the isotopic T\ensuremath{\uparrow}-H\ensuremath{\uparrow} mixture, complete phase separation in its ground state is observed.

Vittorio Penna, Andrea Richaud

We investigate the phase separation mechanism of bosonic binary mixtures in spatially-fragmented traps, evidencing the emergence of phases featuring a different degree of mixing. The analysis is initially carried out by means of a semiclassical approach which transparently shows the occurrence of critical phenomena. These predictions are actually corroborated by the study of genuinely quantum indicators, including, but not limited to, the energy levels' structure and the entanglement between the species. The scope of our work goes also beyond the ground state's properties, as it comprises excited states and the dynamical evolution thereof. In particular, after introducing an indicator to monitor the degree of mixing, we show that several dynamical regimes feature persistent demixing in spite of their remarkably chaotic character.