Meir Ziv, Sikorsky Tomas, Ben-Shlomi Ruti, Akerman Nitzan, Dallal Yehonatan, Ozeri Roee
Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel.
Phys Rev Lett. 2016 Dec 9;117(24):243401. doi: 10.1103/PhysRevLett.117.243401. Epub 2016 Dec 7.
Ultracold atom-ion mixtures are gaining increasing interest due to their potential applications in ultracold and state-controlled chemistry, quantum computing, and many-body physics. Here, we studied the dynamics of a single ground-state cooled ion during few, to many, Langevin (spiraling) collisions with ultracold atoms. We measured the ion's energy distribution and observed a clear deviation from the Maxwell-Boltzmann distribution, characterized by an exponential tail, to a power-law distribution best described by a Tsallis function. Unlike previous experiments, the energy scale of atom-ion interactions is not determined by either the atomic cloud temperature or the ion's trap residual excess-micromotion energy. Instead, it is determined by the force the atom exerts on the ion during a collision which is then amplified by the trap dynamics. This effect is intrinsic to ion Paul traps and sets the lower bound of atom-ion steady-state interaction energy in these systems. Despite the fact that our system is eventually driven out of the ultracold regime, we are capable of studying quantum effects by limiting the interaction to the first collision when the ion is initialized in the ground state of the trap.
超冷原子 - 离子混合物因其在超冷和状态可控化学、量子计算以及多体物理中的潜在应用而受到越来越多的关注。在此，我们研究了单个基态冷却离子在与超冷原子发生少量到大量朗之万（螺旋）碰撞过程中的动力学。我们测量了离子的能量分布，并观察到其明显偏离麦克斯韦 - 玻尔兹曼分布，其特征为指数尾部，转而呈现出由Tsallis函数最佳描述的幂律分布。与先前的实验不同，原子 - 离子相互作用的能量尺度既不由原子云温度也不由离子阱残余过量微运动能量决定。相反，它由碰撞期间原子对离子施加的力决定，该力随后被阱动力学放大。这种效应是离子保罗阱所固有的，并设定了这些系统中原子 - 离子稳态相互作用能量的下限。尽管我们的系统最终会被驱动出超冷状态，但当离子在阱的基态初始化时，我们能够通过将相互作用限制在第一次碰撞来研究量子效应。
