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arXiv 1802.08261cond-mat.str-el
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复合费米液体的Pomeranchuk不稳定性

Pomeranchuk Instability of Composite Fermi Liquids

Kyungmin Lee, Junping Shao, Eun-Ah Kim, F. D. M. Haldane, Edward H. Rezayi

摘要:

量子霍尔系统中的向列性已经在实验上很好地建立在激发朗道能级上。然而,对称性破缺的机制仍然是未知的。在角动量$\ell=2$通道中费米液体参数$F_{\ell} \le -1$的Pomeranchuk不稳定性被认为是相关的机制,但没有明确的理论证明。本文用变分蒙特卡罗方法计算了有限层宽复合费米子费米液体的费米液体参数$F_\ell$。我们考虑了不同朗道能级$n=0,1,2$中的$F_{\ell}$作为层宽参数$η$的函数。我们发现,不像最低的朗道水平,这表明没有Pomeranchuk不稳定的迹象,更高的朗道水平下的$η$的临界值显示Pomeranchuk不稳定。此外,对于$n=2$ Landau能级,临界值$η_c$更高,这与仅在$n=2$ Landau能级中在环境条件下观察到的无序相一致。从我们的工作中出现的画面是,接近真正的2D极限带来了半充满更高的朗道能级系统的边缘Pomeranchuk不稳定性。

英文摘要:

Nematicity in quantum Hall systems has been experimentally well established at excited Landau levels. The mechanism of the symmetry breaking, however, is still unknown. Pomeranchuk instability of Fermi liquid parameter $F_{\ell} \le -1$ in the angular momentum $\ell=2$ channel has been argued to be the relevant mechanism, yet there are no definitive theoretical proofs. Here we calculate, using the variational Monte Carlo technique, Fermi liquid parameters $F_\ell$ of the composite fermion Fermi liquid with a finite layer width. We consider $F_{\ell}$ in different Landau levels $n=0,1,2$ as a function of layer width parameter $η$. We find that unlike the lowest Landau level, which shows no sign of Pomeranchuk instability, higher Landau levels show nematic instability below critical values of $η$. Furthermore, the critical value $η_c$ is higher for the $n=2$ Landau level, which is consistent with observation of nematic order in ambient conditions only in the $n=2$ Landau levels. The picture emerging from our work is that approaching the true 2D limit brings half-filled higher Landau-level systems to the brink of nematic Pomeranchuk instability.

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