Ultracold chromium atoms: from Feshbach resonances to a dipolar Bose–Einstein condensate
Ultracold chromium atoms: from Feshbach resonances to a dipolar Bose–Einstein condensate
复制标题
超冷铬原子：从费什巴赫共振到偶极玻色-爱因斯坦凝聚
DOI：
10.1080/09500340600677088
复制
发表时间：
2007
影响因子：
1.3
通讯作者：
T. Pfau
中科院分区：
文献类型：
--
作者：
J. Stuhler;A. Griesmaier;J. Werner;T. Koch;M. Fattori;T. Pfau
我们报道了超冷铬原子的实验。在交叉光学偶极阱（CODT）中制备52Cr原子云，并施加4至600 G的磁场，我们观察到在不同的磁场值下原子损失增加，从而观察到14个费希巴赫共振。与只考虑偶极子-偶极子耦合的理论比较表明，实验和理论共振位置之间非常吻合，并允许我们提取所涉及分子势的s波散射长度A 6=112(14) A 0, A 4= 58(6) A 0, A 2=−7(20)A 0以及色散系数C 6= 733(70) au和au。589 G处最强的共振计算宽度为1.7 G，三体损失系数小于l3，最大值为~ 3×10−36 m6 s−1。CODT内进一步的蒸发冷却导致玻色-爱因斯坦凝聚态（BEC）的形成，其中有多达10万个凝聚态原子。铬原子之间的磁偶极子-偶极子相互作用是如此强烈，以至于作为偶极子-偶极子相互作用的第一个力学表现，我们观察到冷凝膨胀的修正取决于原子磁偶极子相对于CODT轴的排列。这种磁致伸缩效应与偶极量子气体理论非常吻合，表明Cr-BEC是研究简并态量子气体中偶极-偶极相互作用的良好模型系统。
We report on experiments with ultracold chromium atoms. Preparing a cloud of 52Cr atoms in a crossed optical dipole trap (CODT) and applying magnetic fields between 4 and 600 G, we observe 14 Feshbach resonances by the occurrence of increased atom loss at distinct magnetic field values. A comparison with theory taking only dipole–dipole coupling into account shows very good agreement between experimental and theoretical resonance positions and allows us to extract the s-wave scattering lengths a 6=112(14) a 0, a 4= 58(6) a 0, a 2=−7(20) a 0 of the involved molecular potentials as well as the dispersion coefficients C 6= 733(70) au and au. The strongest resonance at 589 G has a calculated width of 1.7 G and reveals a three-body loss coefficient below L 3, max∼3×10−36 m6 s−1. Further evaporative cooling within the CODT leads to the formation of a Bose–Einstein condensate (BEC) with up to 100 000 condensed atoms. The magnetic dipole–dipole interaction between the Cr atoms is so strong that, as a first mechanical manifestation of dipole–dipole interaction, we observe a modification of the condensate expansion which depends on the alignment of the atomic magnetic dipoles with respect to the axis of the CODT. This magnetostrictive effect is in very good agreement with the theory of dipolar quantum gases and shows that a Cr-BEC is an excellent model system to study dipole–dipole interactions in degenerate quantum gases.