Summary form only given. In the present work, we report experimental results that clearly demonstrate dynamical phenomena beyond the usual approximations applied to time-orbiting-potential (TOP) traps. The paper is organized as follows: After a brief review of the theory of TOP-traps we describe our experimental apparatus and procedure. In the following sections, experimental results and theoretical considerations concerning the breakdown of the time-averaging and the adiabatic approximations are presented. Finally, we summarize our results and discuss the importance of our findings for atom-trapping and BEC experiments.Summary form only given. In the present work, we report experimental results that clearly demonstrate dynamical phenomena beyond the usual approximations applied to time-orbiting-potential (TOP) traps. The paper is organized as follows: After a brief review of the theory of TOP-traps we describe our experimental apparatus and procedure. In the following sections, experimental results and theoretical considerations concerning the breakdown of the time-averaging and the adiabatic approximations are presented. Finally, we summarize our results and discuss the importance of our findings for atom-trapping and BEC experiments.

Quantum Electronics and Laser Science ConferenceNov 13, 20020 citations

Spin in a time-dependent magnetic field

A.A. Lushnikov

Physics Letters AAug 1, 19730 citations

A New Approach to Spin Evolution in Time-Dependent Magnetic Field

杨进 YANG Jin, Lin Nengjie, 张德培 ZHANG De-pei +1 more

Acta Sinica Quantum OpticaJan 1, 20160 citations

Repulsive Fermi gas in a harmonic trap: Ferromagnetism and spin textures

Lindsay J. LeBlanc, Joseph H. Thywissen, A. A. Burkov +1 more

We study ferromagnetism in a repulsively interacting two-component Fermi gas in a harmonic trap. Within a local density approximation, the two components phase separate beyond a critical interaction strength, with one species having a higher density at the trap center. We discuss several easily observable experimental signatures of this transition. The mean-field release energy, its separate kinetic and interaction contributions, as well as the potential energy all depend on the interaction strength and contain a sharp signature of this transition. In addition, the conversion rate of atoms to molecules, arising from three-body collisions, peaks at an interaction strength just beyond the ferromagnetic transition point. We then go beyond the local density approximation and derive an energy functional that includes a term that depends on the local magnetization gradient and acts as a ``surface tension.'' Using this energy functional, we numerically study the energetics of some candidate spin textures that may be stabilized in a harmonic trapping potential at zero net magnetization. We find that a hedgehog state has a lower energy than an ``in-out'' domain-wall state in an isotropic trap. Upon inclusion of trap anisotropy we find that the hedgehog magnetization profile gets distorted due to the surface tension term, this distortion being more apparent for small atom numbers. We estimate that the magnetic dipole interaction does not play a significant role in this system. We consider possible implications for experiments on trapped $^{6}\text{L}\text{i}$ and $^{40}\text{K}$ gases.We study ferromagnetism in a repulsively interacting two-component Fermi gas in a harmonic trap. Within a local density approximation, the two components phase separate beyond a critical interaction strength, with one species having a higher density at the trap center. We discuss several easily observable experimental signatures of this transition. The mean-field release energy, its separate kinetic and interaction contributions, as well as the potential energy all depend on the interaction strength and contain a sharp signature of this transition. In addition, the conversion rate of atoms to molecules, arising from three-body collisions, peaks at an interaction strength just beyond the ferromagnetic transition point. We then go beyond the local density approximation and derive an energy functional that includes a term that depends on the local magnetization gradient and acts as a ``surface tension.'' Using this energy functional, we numerically study the energetics of some candidate spin textures that may be stabilized in a harmonic trapping potential at zero net magnetization. We find that a hedgehog state has a lower energy than an ``in-out'' domain-wall state in an isotropic trap. Upon inclusion of trap anisotropy we find that the hedgehog magnetization profile gets distorted due to the surface tension term, this distortion being more apparent for small atom numbers. We estimate that the magnetic dipole interaction does not play a significant role in this system. We consider possible implications for experiments on trapped $^{6}\text{L}\text{i}$ and $^{40}\text{K}$ gases.

arXiv:0903.5343Physical Review AJul 13, 200968 citations

Time-Dependent Perturbation Expansions

WORLD SCIENTIFIC eBooksNov 1, 20210 citations

Mean field ground state of a spin-1 condensate in a magnetic field

Wenxian Zhang, Su Yi, Li You

We revisit the topic of the mean field ground state of a spin-1 atomic condensate inside a uniform magnetic field ( B ) under the constraints that both the total number of atoms ( N ) and the magnetization ( ) are conserved. In the presence of an internal state (spin component) independent trap, we also investigate the dependence of the so-called single spatial mode approximation on the magnitude of the magnetic field and . Our results indicate that the quadratic Zeeman effect is an important factor in balancing the mean field energy from elastic atom–atom collisions that are known to conserve both N and .We revisit the topic of the mean field ground state of a spin-1 atomic condensate inside a uniform magnetic field ( B ) under the constraints that both the total number of atoms ( N ) and the magnetization ( ) are conserved. In the presence of an internal state (spin component) independent trap, we also investigate the dependence of the so-called single spatial mode approximation on the magnitude of the magnetic field and . Our results indicate that the quadratic Zeeman effect is an important factor in balancing the mean field energy from elastic atom–atom collisions that are known to conserve both N and .

arXiv:cond-mat/0306076New Journal of PhysicsJun 18, 2003117 citations

^{6}\text{L}\text{i}

and

^{40}\text{K}

gases.