Macrocoherence in bilayer quantum Hall state

首次测量和比较了朗道能级填充因子ν=2的双层量子霍尔态和ν=1的单层量子霍尔态下的Skyrmion激发。在具有大隧道能隙的双层样品中观察到的翻转自旋数NS为14，在具有小隧道能隙的双层样品中为NS=7，而在单层样品中为NS=7。在下一阶段，我们通过改变总电子密度和两层之间的密度差，测量了填充因子ν=2/3时双层量子点的磁电阻效应。三种不同的QH态被两种类型的相变分开：一种是自旋相变，另一种是赝旋相变。此外，还检测到两种不同的滞后现象，其中一种是双层体系特有的。相变和磁滞可以用一个推广到双层系统的复合费米子模型很好地描述。

Skyrmion excitations were measured and compared for the first time in the bilayer quantum Hall (QH) state at the Landau-level filling factor ν=2 and in the monolayer QH state at ν=1. The observed number of flipped spins, Ns, is 14 in the bilayer sample with a large tunneling gap, and Ns=7 in the bilayer sample with a small tunneling gap, while it is Ns=7 in the monolayer sample. The difference is interpreted to be due to the interlayer exchange interaction.In the next stage, we measured the magnetoresistance of bilayer QH effects at the fractional filling factor ν=2/3 by changing the total electron density and the density difference between two layers. Three different QH states were separated by two types of phase transition : One is the spin transition and the other is the pseudospin transition. In addition, two different hystereses were detected, one of which is specific to bilayer systems. The phase transitions and the hystereses are described well by a composite fermion model extended to a bilayer system.