Northwestern University, Evanston, Illinois 60208, USA.
Phys Rev Lett. 2018 Dec 21;121(25):255303. doi: 10.1103/PhysRevLett.121.255303.
The direction of the orbital angular momentum of the B phase of superfluid ^{3}He can be controlled by engineering the anisotropy of the silica aerogel framework within which it is imbibed. In this work, we report our discovery of an unusual and abrupt "orbital-flop" transition of the superfluid angular momentum between orientations perpendicular and parallel to the anisotropy axis. The transition has no hysteresis, warming or cooling, as expected for a continuous thermodynamic transition, and is not the result of a competition between strain and magnetic field. This demonstrates the spontaneous reorientation of the order parameter of an unconventional BCS condensate.
超流 ^{3}He 的 B 相的轨道角动量的方向可以通过工程化改变其浸润的二氧化硅气凝胶框架的各向异性来控制。在这项工作中，我们报告了一个不寻常的和突然的超流角动量在垂直和平行于各向异性轴的方向之间的“轨道翻转”转变。如预期的连续热力学转变一样，该转变没有滞后、升温或降温，也不是应变和磁场竞争的结果。这证明了非常规 BCS 凝聚体的序参量的自发重取向。
