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arXiv 2406.09050cond-mat.str-elcond-mat.mes-hall
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通过临界性实现复合费米子的拓扑配对

Topological pairing of composite fermions via criticality

N. Nešković, I. Vasić, M. V. Milovanović

AI总结:

本研究利用有效偶极子表示揭示5/2填充分数量子霍尔效应中复合费米子的拓扑配对起源,解析了马约拉纳费米子解禁闭的临界点,并阐明相互作用形式对系统配对倾向的影响。

摘要:

填充因子为偶分母5/2的分数量子霍尔效应(FQHE)的存在与电子统计要求分母必须为奇数的预期相悖。学界认为,其底层准粒子——复合费米子(CFs)的库珀配对可解释这一效应。此类态应具有BCS波函数的Pfaffian形式(因无自旋),且其可能的类涡旋激发具有非阿贝尔统计特性(源于配对的p波性质)。本文利用该问题的有效偶极子表示揭示了配对的起源,表明配对被编码在描述电荷密度与偶极子(即CFs的流)相互作用的哈密顿量中。配对态存在的必要条件是费米能级处的有效偶极子物理,这源于电子所处的理想能带——朗道能级(LL)的非平凡拓扑;配对态是对不稳定临界行为的一种解决方案,该临界行为的特征是:由于拓扑效应,费米能级处的关联空穴相对于电子(进而相对于偶极子)发生远离。我们解析描述了这一解禁闭临界点,在此临界点上会发生马约拉纳中性费米子的解禁闭。在朗道能级内部存在大的短程排斥相互作用时,临界行为可被稳定为正则化的类费米液体(FLL)态,类似于最低朗道能级(LLL)中的物理特征,但一般而言,对于赝势衰减缓慢的相互作用,系统更易发生配对。

英文摘要:

The fractional quantum Hall effect (FQHE) at the filling factor with an even denominator, 5/2, occurs despite the expectation, due to the electron statistics, that the denominator must be an odd number. It is believed that the Cooper pairing of underlying quasiparticles, composite fermions (CFs), leads to the explanation of this effect. Such a state should have a Pfaffian form of the BCS wave function (due to the absence of spin) and non-Abelian statistics of possible vortex-like excitations (due to the $p$-wave nature of the pairing). Here we expose the origin of pairing by using the effective dipole representation of the problem and show that pairing is encoded in a Hamiltonian that describes the interaction of the charge density with dipoles i.e. the current of CFs. The necessary condition for the paired state to exist is the effective dipole physics at the Fermi level as a consequence of the non-trivial topology of the ideal band in which electrons live - a Landau level (LL); the paired state is a resolution of the unstable, critical behaviour characterized by the distancing of correlation hole with respect to electron (and thus dipole) at the Fermi level due to the topology. We describe analytically this deconfined critical point, at which deconfinement of Majorana neutral fermions takes place. In the presence of large, short-range repulsive interaction inside a LL, the critical behavior may be stabilized into a regularized Fermi-liquid-like (FLL) state, like the one that characterizes the physics in the lowest LL (LLL), but in general, for an interaction with slowly decaying pseudopotentials, the system is prone to pairing.

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