复合费米海的Valley Stoner不稳定性
Valley Stoner Instability of the Composite Fermi Sea
摘要：
我们研究了砷化铝（AlAs）量子阱中最低朗道能级的双组分电子在总填充因子$ν_T=1/2$下的各向异性质量张量和主轴旋转$π/2$。结合精确对角化和密度矩阵重整化群，我们证明了该系统经历了量子相变从一个无隙状态，其中两种口味是同样的填充到另一个无隙状态，其中所有的电子自发地进入一个单一的味道超过了{ \bf $m_x/m_y \sim 7$ }的临界质量各向异性。我们提出这种相变是一种形式的巡回Stoner过渡之间的两个组件和一个单组件的复合费米海状态，并描述了一组试验波函数，成功地捕获量子数和壳填充效应在有限尺寸系统，以及提供了一个物理图片，这些国家的能量。我们的估计表明，复合费米海的铝是一个巡回斯通纳磁铁与有限的自发谷极化的模拟。我们查明的实验证据表明存在的斯通纳磁性的耆那教国家周围$ν=1/2$。
英文摘要：
We study two-component electrons in the lowest Landau level at total filling factor $ν_T=1/2$ with anisotropic mass tensors and principal axes rotated by $π/2$ as realized in Aluminum Arsenide (AlAs) quantum wells. Combining exact diagonalization and the density matrix renormalization group we demonstrate that the system undergoes a quantum phase transition from a gapless state in which both flavors are equally populated to another gapless state in which all the electrons spontaneously polarize into a single flavor beyond a critical mass anisotropy of {\bf $m_x/m_y \sim 7$}. We propose that this phase transition is a form of itinerant Stoner transition between a two-component and a single-component composite fermi sea states and describe a set of trial wavefunctions which successfully capture the quantum numbers and shell filling effects in finite size systems as well as providing a physical picture for the energetics of these states. Our estimates indicate that the composite Fermi sea of AlAs is the analog of an itinerant Stoner magnet with a finite spontaneous valley polarization. We pinpoint experimental evidence indicating the presence of Stoner magnetism in the Jain states surrounding $ν=1/2$.
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