论文标题
强大的量子厅铁磁磁性靠近门口的ν= 1 Landau级过境
Robust Quantum Hall Ferromagnetism near a Gate-Tuned ν = 1 Landau Level Crossing
论文作者
论文摘要
在低尺度的二维电子系统中，当在费米水平上有两个相反的自旋或伪旋转交叉的Landau级别时，交换能的优势可以导致铁磁，量子霍尔的基础状态，其间隙由交换能量确定，并以skyrmions为兴奋。这通常是通过施加静水压力或单轴应变来实现的。我们在这里研究了一个非常高质量的，低密度，二维孔系统，仅限于30 nm宽（001）GAAS量子井，其中两个最低能量的Landau水平可以调节以跨越填充因子$ν= 1 $。当我们通过更改孔密度从$ν= 1 $的一侧调整过交叉的场位置时，Quantum Hall状态为$ν= 1 $的能量差距仍然非常大，并且仅在交叉点附近显示出一个小倾角。总体差距遵循$ \ sqrt {b} $依赖性，预期的是交换能源。我们的数据与强大的量子霍尔铁磁铁作为基态一致。
In a low-disorder two-dimensional electron system, when two Landau levels of opposite spin or pseudospin cross at the Fermi level, the dominance of the exchange energy can lead to a ferromagnetic, quantum Hall ground state whose gap is determined by the exchange energy and has skyrmions as its excitations. This is normally achieved via applying either hydrostatic pressure or uniaxial strain. We study here a very high-quality, low-density, two-dimensional hole system, confined to a 30-nm-wide (001) GaAs quantum well, in which the two lowest-energy Landau levels can be gate tuned to cross at and near filling factor $ν=1$. As we tune the field position of the crossing from one side of $ν=1$ to the other by changing the hole density, the energy gap for the quantum Hall state at $ν=1$ remains exceptionally large, and only shows a small dip near the crossing. The gap overall follows a $\sqrt{B}$ dependence, expected for the exchange energy. Our data are consistent with a robust quantum Hall ferromagnet as the ground state.
