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arXiv 2006.06925cond-mat.mes-hallcond-mat.str-el
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偶分母分数量子霍尔态的厚度效应和自旋极化

Finite-thickness effect and spin polarization of the even-denominator fractional quantum Hall states

Pengjie Wang, Jian Sun, Hailong Fu, Yijia Wu, Hua Chen, L. N. Pfeiffer, K. W. West, X. C. Xie, Xi Lin

摘要:

第二朗道能级(LL)中自旋极化的偶分母分数量子霍尔(Fractional quantum Hall,简称FHH)态,即5/2和7/2,可能具有服从非阿贝尔统计的新型准粒子激发.然而,7/2 H态的自旋极化还没有被实验研究,而倾斜场实验中5/2 H态的自旋极化仍然存在争议。利用最低电子温度为25 mK的压电驱动样品旋转器,通过精确控制倾斜角,研究了第二LL中偶分母1H态的能隙,分辨率小于0.1°。我们观察到两种不同的能隙对面内磁场的依赖性,5/2,7/2,其他的量子霍尔态(7/3和8/3)在第二LL和重入整数量子霍尔(RIQH)态在第三LL。虽然跃迁场随态的不同而不同,但它们对应的面内磁长度与样品的量子阱厚度相当,这可能是由于有限厚度效应的影响。在低的面内磁场下,在受限的有限厚度效应开始占主导地位之前,5/2和7/2态的能隙都显示出非减小的行为,支持自旋极化的基态。我们的结果还表明,第三个LL中的7/3,8/3H_2OH态和RIQH态是自旋极化或部分自旋极化的。

英文摘要:

The spin-polarized even-denominator fractional quantum Hall (FQH) states in the second Landau level (LL), i.e. 5/2 and 7/2, may possess novel quasi-particle excitations obeying non-Abelian statistics. However, the spin polarization of the 7/2 FQH state has not been investigated experimentally and the spin polarization of the 5/2 FQH state from tilted field experiments remains controversial. Using a piezo-driven sample rotator with the lowest electron temperature down to 25 mK, we studied the energy gap of the even-denominator FQH states in the second LL by precise control of the tilted angles with a resolution less than 0.1°. We observed two different energy gap dependences on the in-plane magnetic field for 5/2, 7/2, other FQH states (7/3 and 8/3) in the second LL and reentrant integer quantum Hall (RIQH) states in the third LL. Though the transition fields vary from states, their corresponding in-plane magnetic lengths are comparable to the quantum well thickness of the sample, which may result from the influence of the finite-thickness effect. At low in-plane magnetic fields, before the conjectured finite-thickness effect starts to dominate, the energy gaps of both 5/2 and 7/2 states show a non-decreasing behavior, supporting spin-polarized ground states. Our results also suggest that the 7/3, 8/3 FQH states, and the RIQH states in the third LL are spin-polarized or partially spin-polarized.

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