人工磁场下各向异性偶极玻色气体的量子相变

Quantum phase transitions of anisotropic dipolar bosons under artificial magnetic field

光晶格中的冷原子系统是实现量子模拟和量子计算的有效平台之一,其相变特性的研究有助于系统中新奇量子态物理机制的探索和实验观测.本文利用朗道相变理论和非均匀平均场方法,研究了人工磁场下光晶格中各向异性偶极玻色气体的相变,得到了系统不可压缩相(Mott绝缘相、棋盘或条纹密度波相)-可压缩相(超流、棋盘或条纹超固相)的解析相变条件,给出了系统的完整相图.有趣的是,各向异性偶极相互作用会使得系统中的棋盘密度波相和棋盘超固相变为条纹密度波相和条纹超固相,人工磁场会稳定绝缘相和超固相,使得绝缘相和超固相在相图中的存在区域变大.此外,引入外加谐振势后发现系统中的不同量子相可以共存.

The quantum system composed of optical lattice and ultracold atomic gas is an ideal platform for realizing quantum simulation and quantum computing.Especially for dipolar bosons in optical lattices with artificial gauge fields,the interplay between anisotropic dipolar interactions and artificial gauge fields leads to many novel phases.Exploring the phase transition characteristics of the system is beneficial to understanding the physics of quantum many-body systems and observing quantum states of dipolar system in experiments.In this work,we investigate the quantum phase transitions of anisotropic dipolar bosons in a two-dimensional optical lattice with an artificial magnetic field.Using an inhomogeneous mean-field method and a Landau phase transition theory,we obtain complete phase diagrams and analytical expressions for phase boundaries between an incompressible phase and a compressible phase.Our results show that both the artificial magnetic field and the anisotropic dipolar interaction have a significant effect on the phase diagram.When the polar angle increases,the system undergoes the phase transition from a checkerboard supersolid to a striped supersolid.For small polar angle(V_(x)/U=0.2,V_(y)/U=0.1,Fig.(a)),artificial magnetic field induces both checkerboard solid phase and supersolid phase to extend to a large hopping region.For a larger polar angle(V_(x)/U=0.2,V_(y)/U=-0.1,Fig.(b)),artificial magnetic field induces both striped solid and striped supersolid to extend to a large hopping region.Thus,the artificial magnetic field stabilizes the density wave and supersolid phases.In addition,we reveal the coexistence of different quantum phases in the presence of an external trapping potential.The research results provide a theoretical basis for manipulating the quantum phase in experiments on anisotropic dipolar atoms by using an artificial magnetic field.