Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
Phys Rev Lett. 2013 May 3;110(18):186802. doi: 10.1103/PhysRevLett.110.186802. Epub 2013 Apr 29.
We study quantum Hall ferromagnets with a finite density of topologically charged spin textures in the presence of internal degrees of freedom such as spin, valley, or layer indices, so that the system is parametrized by a d-component spinor field. In the absence of anisotropies we find a hexagonal Skyrmion lattice that completely breaks the underlying SU(d) symmetry with the low-lying excitation spectrum separating into d(2) - 1 gapless acoustic magnetic modes and a magnetophonon. The ground state charge density modulations, which inevitably exist in these lattices, vanish exponentially in d. We discuss the role of effective mass anisotropy for SU(3)-valley Skyrmions relevant to experiments with AlAs quantum wells. Here we find a transition which breaks a sixfold rotational symmetry of the triangular lattice, followed by the formation of a square lattice at large values of anisotropy strength.
我们研究了具有有限拓扑电荷自旋纹理密度的量子霍尔铁磁体，这些自旋纹理存在于自旋、谷或层指数等内部自由度中，因此系统由一个 d 分量旋量场参数化。在没有各向异性的情况下，我们发现了一个六边形 Skyrmion 晶格，它完全打破了基本的 SU(d)对称性，低能激发谱分为 d(2) - 1 无间隙声磁模式和磁声子。这些晶格中不可避免存在的基态电荷密度调制在 d 中呈指数衰减。我们讨论了有效质量各向异性对与 AlAs 量子阱实验相关的 SU(3)-谷 Skyrmions 的作用。在这里，我们发现了一个打破三角形晶格六重旋转对称性的相变，随后在各向异性强度较大时形成了一个正方形晶格。
