Quantum Kármán Vortex Street In A Two-Component Dipolar Bose-Einstein Condensate

Bose-Einstein condensate(BEC)is a gaseous,superfluid state of matter taking place if the temperature at close to absolute zero.Since the BEC was first experimentally achieved in 1995,It has provided a clean and precisely regulated platform for studying quantization vortices in superfluids.Due to the interaction between components and components,the two-component BEC shows a lot of novel phenomena.Kármán vortex street is a traditional problem in classical fluids.It refers to the fact that when the steady incoming flow circumvents some obstacle under certain conditions,the two sides of the obstacle will periodically shed regular double-row vortex with opposite rotation direction.According to von Kármán’s theory,once formed,vortex streets exist for a long time in non-viscous fluids.Therefore,it is particularly important to study quantum Karman vortex street in inviscid quantum fluid.Based on this,this paper focuses on "Quantum Kármán vortex street in two-component dipolar Bose-Einstein Condensate".For the study of Kármán vortex streets and their dynamics in two-component dipolar BEC systems,generally speaking,based on the mean field approximation,two component coupled Gross Pitaevskii(GP)equations can be used to describe the dynamics of the system.In this paper,the wake of the moving obstacle potential in the two-component dipolar BEC and the phase-separated two-component dipolar BEC are studied by numerical simulation of coupled GP equations.we find the ground state of the two-component dipolar BEC system composed of 164Dy and 168Er by the imaginary-time propagation method approach with initial conditions.Then,the time-splitting spectral method is employed to make the nonlinear dynamical evolution with periodic boundary conditions,where the initial state is adopted as the ground state obtained.The staggered quantum Karman vortex streets of the two components appear in different positions respectively,which is called out-sync quantum Kármán vortex street.In the phase-separated two-component dipolar BEC system composed of two different hyperfine states of 52Cr atoms,ghost vortex street composed of ghost vortex appears.There are other types of vortex shedding modes in different two-component dipolar BEC,such as vortex dipoles,V-shaped vortex dipoles,and quantum turbulence.The calculation results of the drag force acting on the moving obstacle potential shows that the shedding of vortices contributes to the generation of drag force on the moving obstacle potential,and the greater the dipolar interaction,the greater the average drag force acting on the moving obstacle potential.In the two-component dipolar BEC of mixed phase state,the parameter range of the out-sync quantum Karman vortex street is also affected by the intensity of the dipolar interaction.When the dipolar interaction is stronger,the parameter range of the out-sync quantum Karman vortex street is smaller,and the dipolar interaction will change the order of the emergence of the vortex modes.