Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.
School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA.
Nat Nanotechnol. 2016 Apr;11(4):345-51. doi: 10.1038/nnano.2015.293. Epub 2016 Jan 18.
The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov-Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode.
在拓扑绝缘体纳米线或纳米带中，螺旋狄拉克费米子拓扑表面态有望实现新型拓扑器件和奇异物理，如马约拉纳费米子。在这里，我们报告了在 Bi2Te3 拓扑绝缘体纳米带中进行的局域和非局域输运测量，这些纳米带表现出长达约 2μm 的弹道输运。电导与轴向磁场 Φ 的关系表现出阿哈罗诺夫-玻姆（Aharonov-Bohm）振荡，其最大值在半整数或整数磁通量子（Φ0=h/e，其中 h 是普朗克常数，e 是电子电荷）处交替出现，这取决于周期性地由栅极调谐费米波矢（kF）决定，周期为 2π/C（其中 C 是纳米带的周长）。电导与栅极电压的关系也表现出 kF 周期性振荡，在 Φ=0 和 Φ0/2 之间呈反相关。这些振荡使我们能够探测 Bi2Te3 的能带结构，并且与周期性地量子化的拓扑表面态形成一系列一维子带一致，这些子带随着无带隙狄拉克点的出现/消失，伴随着一维自旋螺旋模式，经历周期性的磁场诱导拓扑转变。
