Coupling of Coexisting Quantum States

Qi Gu, Xiaoling Cui

The authors propose a spin-twist scheme for engineering a liquid-gas transition and the coexistence of interacting bosons at zero temperature. They demonstrate the scheme for ultracold binary bosons subject to Rabi coupling and magnetic detuning, where the liquid-gas transition and coexistence can be conveniently tuned and characterized.

Alto Osada, Rekishu Yamazaki, Atsushi Noguchi

Zu‐Jian Ying, Mario Cuoco, Canio Noce +1 more

We investigate the conditions for the occurrence of the coexisting phases that exhibit singlet superconductivity and itinerant ferromagnetism arising from spin asymmetric bandwidths. The exact solution for a reduced BCS pairing model with spin dependent bandwidths is used to determine the ground-state diagram as a function of the coupling parameter, the total density, and the topology of the single-particle spectrum. A spin-polarized superconducting state is obtained in the regime of large pair couplings with a strong bandwidth asymmetry. The analysis reveals that, for such a type of ferromagnetism, small (large) values of the density of states at energies close to the edges of the band enhance (hinder) the tendency toward a coexistence of strong pairing correlations and finite spin polarizations.

Jing-Min Zhu

For matrix product states of one-dimensional spin-1/2 chains, we investigate the properties of quantum phase transition of the proposed composite system. We find that the system has three different ferromagnetic phases, one line of the two ferromagnetic phases coexisting equally describes the paramagnetic state, and the other two lines of two ferromagnetic phases coexisting equally describe the ferrimagnetic states, while the three phases coexisting equally point describes the ferromagnetic state. Whether on phase transition lines or at the phase transition point, the system is always in an isolated mediate-coupling state, the physical quantities are discontinuous and the system has long-range correlation and has long-range classical correlation and long-range quantum correlation. We believe that our work is helpful for comprehensively and profoundly understanding the quantum phase transitions, and of some certain guidance and enlightening on the classification and measure of quantum correlation of quantum many-body systems.

Stanley Gudder