Controlling the interactions Near charge neutrality and subject to perpendicular magnetic fields, graphene is expected to become a ferromagnet with edge states not unlike those in two-dimensional topological insulators. Observing this effect experimentally has proven tricky because very large magnetic fields are needed to overcome the effect of electron-electron interactions, which drive the system to competing states. Instead of amping up the field, Veyrat et al. placed their graphene samples on a substrate made out of strontium titanate, which effectively screened the interactions. Transport measurements confirmed the formation of the characteristic edge states. Science, this issue p. 781 Transport measurements in graphene indicate edge states similar to those in 2D topological insulators. The ground state of charge-neutral graphene under perpendicular magnetic field was predicted to be a quantum Hall topological insulator with a ferromagnetic order and spin-filtered, helical edge channels. In most experiments, however, an insulating state is observed that is accounted for by lattice-scale interactions that promote a broken-symmetry state with gapped bulk and edge excitations. We tuned the ground state of the graphene zeroth Landau level to the topological phase through a suitable screening of the Coulomb interaction with the high dielectric constant of a strontium titanate (SrTiO3) substrate. Robust helical edge transport emerged at magnetic fields as low as 1 tesla and withstanding temperatures up to 110 kelvin over micron-long distances. This versatile graphene platform may find applications in spintronics and topological quantum computation.

中文翻译：

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SrTiO3 上石墨烯中的螺旋量子霍尔相

控制相互作用接近电荷中性并受到垂直磁场的影响，石墨烯有望成为边缘状态与二维拓扑绝缘体不同的铁磁体。事实证明，通过实验观察这种效应很棘手，因为需要非常大的磁场来克服电子-电子相互作用的影响，而电子-电子相互作用将系统推向竞争状态。Veyrat 等人并没有扩大这个领域。将他们的石墨烯样品放在由钛酸锶制成的基板上，这有效地筛选了相互作用。传输测量证实了特征边缘状态的形成。科学，这个问题 p。781 石墨烯中的传输测量表明边缘状态类似于二维拓扑绝缘体中的边缘状态。垂直磁场下电荷中性石墨烯的基态被预测为具有铁磁有序和自旋过滤螺旋边缘通道的量子霍尔拓扑绝缘体。然而，在大多数实验中，观察到一种绝缘状态，这是由晶格尺度相互作用引起的，这种相互作用促进了具有间隙体和边缘激发的破坏对称状态。我们通过适当筛选库仑相互作用与钛酸锶 (SrTiO3) 衬底的高介电常数，将石墨烯零朗道能级的基态调整到拓扑相。强大的螺旋边缘传输出现在低至 1 特斯拉的磁场中，并在微米长距离内承受高达 110 开尔文的温度。