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arXiv 1502.03446cond-mat.mes-hallhep-th
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复合费米子是狄拉克粒子吗?

Is the Composite Fermion a Dirac Particle?

Dam Thanh Son

摘要:

本文提出了半满朗道能级费米液体基态的粒子-空穴对称理论。这个理论应该适用于磁场中电荷中性的狄拉克费米子,以及在可忽略的朗道能级间混合极限下的非相对论费米子的$ν=\frac12$量子霍尔基态。我们认为,当粒子-空穴对称性是准确的,复合费米子是一个无质量的狄拉克费米子,其特征在于周围的费米圆的$π$的Berry相位。本文给出了这种费米子的有效场论,并讨论了它的离散对称性,特别是$\mathcal C\mathcal P$。狄拉克复合费米子通过规范相互作用,但非陈-西蒙斯相互作用。填充因子为$\frac n{2n+1}$和$\frac{n+1}{2n+1}$的Jain序列态的粒子-空穴共轭对,在传统的复合费米子图像中对应于具有不同填充因子$n$和$n+1$的整数量子霍尔态,现在被映射到狄拉克复合费米子的相同的半整数填充因子$n+\frac12$。我们将Pfizer态和反Pfizer态解释为轨道角动量符号相反的狄拉克费米子的$d$波Bardeen-Cooper-Schrieffer配对态,而$s$波配对将产生粒子-空穴对称的非阿贝尔带隙相位。当粒子-空穴对称性不精确时,狄拉克费米子具有$\mathcal C\mathcal P$破缺质量。传统的费米子陈-西蒙斯理论是在质量理论的非相对论极限下出现的。

英文摘要:

We propose a particle-hole symmetric theory of the Fermi-liquid ground state of a half-filled Landau level. This theory should be applicable for a Dirac fermion in the magnetic field at charge neutrality, as well as for the $ν=\frac12$ quantum Hall ground state of nonrelativistic fermions in the limit of negligible inter-Landau-level mixing. We argue that when particle-hole symmetry is exact, the composite fermion is a massless Dirac fermion, characterized by a Berry phase of $π$ around the Fermi circle. We write down a tentative effective field theory of such a fermion and discuss the discrete symmetries, in particular, $\mathcal C\mathcal P$. The Dirac composite fermions interact through a gauge, but non-Chern-Simons, interaction. The particle-hole conjugate pair of Jain-sequence states at filling factors $\frac n{2n+1}$ and $\frac{n+1}{2n+1}$, which in the conventional composite fermion picture corresponds to integer quantum Hall states with different filling factors, $n$ and $n+1$, is now mapped to the same half-integer filling factor $n+\frac12$ of the Dirac composite fermion. The Pfaffian and anti-Pfaffian states are interpreted as $d$-wave Bardeen-Cooper-Schrieffer paired states of the Dirac fermion with orbital angular momentum of opposite signs, while $s$-wave pairing would give rise to a particle-hole symmetric non-Abelian gapped phase. When particle-hole symmetry is not exact, the Dirac fermion has a $\mathcal C\mathcal P$-breaking mass. The conventional fermionic Chern-Simons theory is shown to emerge in the nonrelativistic limit of the massive theory.

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