Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev Lett. 2018 Jun 22;120(25):256601. doi: 10.1103/PhysRevLett.120.256601.
The enigmatic even-denominator fractional quantum Hall state at Landau level filling factor ν=5/2 is arguably the most promising candidate for harboring Majorana quasiparticles with non-Abelian statistics and, thus, of potential use for topological quantum computing. The theoretical description of the ν=5/2 state is generally believed to involve a topological p-wave pairing of fully-spin-polarized composite fermions through their condensation into a non-Abelian Moore-Read Pfaffian state. There is, however, no direct and conclusive experimental evidence for the existence of composite fermions near ν=5/2 or for an underlying fully-spin-polarized Fermi sea. Here, we report the observation of composite fermions very near ν=5/2 through geometric resonance measurements and find that the measured Fermi wave vector provides direct demonstration of a Fermi sea with full spin polarization. This lends crucial credence to the model of 5/2 fractional quantum Hall effect as a topological p-wave paired state of composite fermions.
在朗道能级填充因子 ν=5/2 处的神秘偶数分数量子霍尔态，可以说是最有希望容纳具有非阿贝尔统计特性的马约拉纳准粒子的候选者，因此可能用于拓扑量子计算。通常认为，对 ν=5/2 态的理论描述涉及全自旋极化复合费米子通过它们凝聚成非阿贝尔摩尔-里德 Pfaffian 态而进行的拓扑 p 波配对。然而，并没有直接和确凿的实验证据表明在 ν=5/2 附近存在复合费米子，或者存在潜在的全自旋极化费米海。在这里，我们通过几何共振测量报告了非常接近 ν=5/2 的复合费米子的观测结果，并发现所测量的费米波矢提供了全自旋极化费米海的直接证明。这为 5/2 分数量子霍尔效应作为复合费米子的拓扑 p 波配对态的模型提供了至关重要的依据。
