近日，美国普林斯顿大学的M. Shayegan&S. K. Singh及其研究团队取得一项新进展。经过不懈努力，他们揭示ν=1/2分数量子霍尔态的Jain态和子态之间的拓扑相变。相关研究成果已于2024年5月27日在国际知名学术期刊《自然—物理学》上发表。

本文报道了在填充因子ν=p/(2p±1)至ν=8/17和9/17的范围内，ν=1/2态被多个Jain序列的复合费米子态所包围的现象。随着研究人员提高电子密度，ν=1/2态的强度得到增强，其能隙增大至4K。同时，令人惊讶的是，8/17和7/13态突然表现出比相邻的高阶分数态更强的特性。值得注意的是，ν=8/17和7/13的状态正是理论上预测的单组分Pfaffian ν=1/2状态的最简单子态。这一发现表明，从Jain序列状态到Pfaffian子状态的转变过程中，8/17和7/13态可能经历了拓扑相变。

据悉，当填充因子ν为1/2时，偶数分母分数量子霍尔态成为二维电子系统中引人注目的多体相，因其独特地出现在基态而非激发态的朗道能级中。在宽量子阱中，电子分布呈现双层电荷结构，层间存在有限的隧穿效应。这种状态是阿贝尔双组分形式还是非阿贝尔单组分形式，自实验发现以来一直存在争议。

附：英文原文

Title: Topological phase transition between Jain states and daughter states of the ν=1/2 fractional quantum Hall state

Author: Singh, S. K., Wang, C., Tai, C. T., Calhoun, C. S., Villegas Rosales, K. A., Madathil, P. T., Gupta, A., Baldwin, K. W., Pfeiffer, L. N., Shayegan, M.

Issue&Volume: 2024-05-27

Abstract: The even-denominator fractional quantum Hall state at a filling factor of ν=1/2 is an intriguing many-body phase in two-dimensional electron systems, as it appears in the ground state rather than an excited Landau level. It is observed in wide quantum wells where the electrons have a bilayer charge distribution with finite tunnelling between the layers. Whether this state takes an Abelian two-component form or a non-Abelian one-component form has been debated since its experimental discovery. Here we report the observation of the ν=1/2 state that is flanked by numerous Jain-sequence composite fermion states at ν=p/(2p±1) up to ν=8/17 and 9/17. As we raise the density, the ν=1/2 state is strengthened, its energy gap increases up to 4K and, at the same time, the 8/17 and 7/13 states abruptly become stronger than their neighbouring high-order fractions. The states at ν=8/17 and 7/13 are the theoretically predicted, simplest daughter states of the one-component Pfaffian ν=1/2 state. This means that our data suggest a topological phase transition of 8/17 and 7/13 states from the Jain-sequence states to the daughter states of the Pfaffian.

DOI: 10.1038/s41567-024-02517-w

Source: https://www.nature.com/articles/s41567-024-02517-w