We calculate the electron spectral functions at the edges of the Moore-Read Pfaffian and anti-Pfaffian fractional quantum Hall states, in the clean limit. We show that their qualitative differences can be probed using momentum resolved tunneling, thus providing a method to unambiguously distinguish which one is realized in the fractional quantum Hall state observed at filling factor $ν=5/2$. We further argue that edge reconstruction, which may be less important in the first excited Landau level (LL) than in the lowest LL, can also be detected this way if present.
We consider electrical and thermal equilibration of the edge modes of the Anti-Pfaffian quantum Hall state at $ν=5/2$ due to tunneling of the Majorana edge mode to trapped Majorana zero modes in the bulk. Such tunneling breaks translational invariance and allows scattering between Majorana and other edge modes in such a way that there is a parametric difference between the length scales for equilibration of charge and heat transport between integer and Bose mode on the one hand, and for thermal equilibration of the Majorana edge mode on the other hand. We discuss a parameter regime in which th…
Quantum Hall Phase Diagram of Half-filled Bilayers in the Lowest and the Second Orbital Landau Levels: Abelian versus Non-Abelian Incompressible Fractional Quantum Hall States
我们研究了半填充双层结构中最低两个朗道能级中分数量子霍尔效应(Fractional quantum Hall effect,FQHE)的量子相图,它是隧穿强度和层间距的函数,即,我们重新审视最低朗道能级填充因子1/2双层问题并做出涉及半填充的第二朗道能级中的双层的新预测(即,填充因子5/2)。使用数值精确对角化,我们调查的重要问题,这个系统是否支持由非阿贝尔摩尔-里德Pfweian状态描述的强隧穿制度的一个非对称性。在最低的朗道水平,我们发现,虽然在原则上,增加(递减)隧穿强度(层分离)可以导致从阿贝尔双组分Halperin 331到非阿贝尔单组分Moore-Read Pfperin状态的转变,在朗道能级最低的Pfronan区域,OHE激发能隙相对较小--我们建立了迄今为止观察到的所有OHE态的一半--填充的最低朗道能级双层最可能由阿贝尔Halperin 331状态描述。在第二个朗道水平,我们作出预测,双层结构将表现出两个不同的分支不可压缩的ECOHE对应的阿贝尔331状态(在中等到低的隧道和大的层分离)和非阿贝尔摩尔-里德Pfavian状态(在大隧道和小的层分离)。这两个分支的观测和它们之间可能的量子相变将是令人信服的证据,支持在第二朗道能级的非阿贝尔Moore-Read Pfronan状态的存在。我们讨论我们的结果在现有的实验和理论工作的背景下。
In this review the physics of Pfaffian paired states, in the context of fractional quantum Hall effect, is discussed using field-theoretical approaches. The Pfaffian states are prime examples of topological ($p$-wave) Cooper pairing and are characterized by non-Abelian statistics of their quasiparticles. Here we focus on conditions for their realization and competition among them at half-integer filling factors. Using the Dirac composite fermion description, in the presence of a mass term, we study the influence of Landau level mixing in selecting a particular Pfaffian state. While Pfaffian an…
Anomalous charge tunneling in the fractional quantum Hall edge states at filling factor ν= 5/2
我们解释了最近在$ν=5/2$ [M. Dolev,Y.真恶心Y C. Chung,M. Heiblum,V. Umansky,and D. Mahalu,Phys.Rev. B. \textbf{81},161303(R)(2010)]。微分电导和过量噪声的实验数据进行拟合,使用反Pfronan模型,通过适当地考虑重整化的Luttinger参数诱导的耦合系统的固有$1/f$噪声。我们表明,一个奇特的凝聚物激发与电荷$e/2$,预期的$e/4$电荷的两倍,占主导地位的低能量下的输运性质。
We present a method for the exact construction of the fully particle-hole symmetric PH-Pfaffian ground state and its charged excitations on a sphere. We adopt the Moore-Read state, but with a nonholomorphic pairing component as in previous studies, and project it to the lowest Landau level. We study the energetics as well as other properties of these states and find that in a pure system interacting with the Coulomb forces the PH-Pfaffian cannot compete with either the Moore-Read state or its particle-hole conjugate, the anti-Pfaffian state, as an explanation for the 5/2-effect.
The recent measurement of a half-integer thermal conductance for the $ν=5/2$ fractional quantum Hall state has confirmed its non-Abelian nature, making the question of the underlying topological order highly intriguing. We analyze the shot noise at the edge of the three most prominent non-Abelian candidate states. We show that the noise scaling with respect to the edge length can, in combination with the thermal conductance, be used to experimentally distinguish between the Pfaffian, anti-Pfaffian, and particle-hole-Pfaffian edge structures.
Fractional quantum Hall quasiparticles are generally characterized by two quantum numbers: electric charge $Q$ and scaling dimension $Δ$. For the simplest states (such as the Laughlin series) the scaling dimension determines the quasiparticle's anyonic statistics (the statistical phase $θ=2πΔ$). For more complicated states (featuring counterpropagating modes or non-Abelian statistics) knowing the scaling dimension is not enough to extract the quasiparticle statistics. Nevertheless, even in those cases knowing the scaling dimension facilitates distinguishing different candidate theories for des…
An important development in the field of the fractional quantum Hall effect has been the proposal that the 5/2 state observed in the Landau level with orbital index $n = 1$ of two dimensional electrons in a GaAs quantum well originates from a chiral $p$-wave paired state of composite fermions which are topological bound states of electrons and quantized vortices. This state is theoretically described by a "Pfaffian" wave function or its hole partner called the anti-Pfaffian, whose excitations are neither fermions nor bosons but Majorana quasiparticles obeying non-Abelian braid statistics. This…
A quantum Hall (QH) interface is different from an ordinary QH edge, as the latter has its location determined by the confining potential, while the former can be unpinned and behave like a free string. In this paper, we demonstrate this difference by studying three different interfaces formed by (i) the Laughlin state and the vacuum, (ii) the Pfaffian state and the vacuum, and (iii) the Pfaffian and the anti-Pfaffian states. We find that string-like interfaces propagating freely in the QH system lead to very different dynamical properties from edges. This qualitative difference gives rise to …
We study the time-dependent dynamical phase of fractional quasiparticles in quantum Hall states using Ramsey interferometry. A Ramsey two-pulse voltage modulation generates an interference term in the current noise of a quantum point contact oscillating with the dynamical phase. We show that the interference pattern probes the Green's function of the fractional quasi-particles in the time domain and reveals the fractional charge. We address both the case of a point-like tunnel junction and the case of momentum-resolved tunneling which also provides information on the speed of those quasipartic…
The coupled-wire construction provides a useful way to obtain microscopic Hamiltonians for various two-dimensional topological phases, among which fractional quantum Hall states are paradigmatic examples. Using the recently introduced flux attachment and vortex duality transformations for coupled wires, we show that this construction is remarkably versatile to encapsulate phenomenologies of hierarchical quantum Hall states: the Jain-type hierarchy states of composite fermions filling Landau levels and the Haldane-Halperin hierarchy states of quasiparticle condensation. The particle-hole conjug…
We numerically study a 5/2 fractional quantum Hall system with even number of electrons using the exact diagonalization where both the strong Landau level (LL) mixing and a finite width of the quantum well have been considered and adapted into a screened Coulomb interaction. With the principal component analysis, we are able to recognize a compressible-incompressible phase transition in the parameter space made of the magnetic field and the quantum well width by the competition between the first two leading components of the ground states wave functions, which is consistent with the low-lying …
Motivated by the experimental observation of a quantized 5/2 thermal conductance at filling $ν=5/2$, a result incompatible with both the Pfaffian and the Antipfaffian states, we have pushed the expansion of the effective Hamiltonian of the $5/2$ quantized Hall state to third-order in the parameter $κ=E_c/\hbar ω_c \propto 1/\sqrt{B}$ controlling the Landau level mixing , where $E_c$ is the Coulomb energy and $ω_c$ the cyclotron frequency. Exact diagonalizations of this effective Hamiltonian show that the difference in overlap with the Pfaffian and the AntiPfaffian induced at second-order is re…