Investigation of the Macro Coherence in Bilayer Quantum Hall State by Micro Wave

研究了双层量子霍尔态的层间相干性。建立了用于约瑟夫森等离子体激元测量的微波低温恒温器，并在2K下进行了实验，观察到了明显的量子霍尔效应，但没有观测到约瑟夫森等离子体激元。我们没有观察到约瑟夫森等离子体激元的原因是由于样品质量较低和温度较高。我们将很快改进检测约瑟夫森等离子激元的实验方法。另一方面，我们从输运方面获得了重要的实验结果。(1)：通过详细的输运测量，我们研究了双层v=1量子霍尔态中的伪自旋(层自由度)磁畴结构。我们发现，磁阻R_&lt；xx&gt；在公度-非公度转变处有一个宽峰。在0K以下的峰值R_&lt；xx&gt；的外推值是有限的，表明存在耗散基态。从R&lt；xx&gt；的B&lt；//&gt；依赖关系和激活能与理论的比较中，我们认为耗散的起因是孤子晶格中的赝旋磁畴壁。这是第一次在量子霍尔态中观察到电阻峰不是由两个朗道能级的交叉引起的，而可能是由许多伪自旋磁区引起的，即层间相位扭曲。(2)：我们研究了总朗道能级填充因子v=1时双层系统中量子霍尔态的各向异性输运。我们发现，在公度态和非公度态之间的相变点，各向异性变得显著。这会导致在过渡周围出现单向状态。

We investigated interlayer coherence of the bilayer quantum Hall states. The microwave cryostat was constructed for measurement of Josephson plasmon and then the experiments were done at 2 K. The quantum Hall effects were clearly observed, but Josephson plasmon was not observed. The cause we cannot observe Josephson plasmon is due to the low quality of the sample and the higher temperature. We will soon improve the experimental way to detect Josephson plasmon. The other hand, we get important experimental results for interlayer coherence from transport.(1) : We study a pseudospin (layer degree of freedom) domain structure in bilayer v=1 quantum Hall states by detailed transport measurements in tilted magnetic fields. We find that the magnetoresistance R_<xx> shows a broad peak at the commensurate-incommensurate transition. An extrapolated value of R_<xx> at the peak down to 0 K is finite, showing the existence of a dissipative ground state. From the comparison of B_<//> dependence of R_<xx> and activation energy with theories, we suggest that the origin of the dissipation is pseudospin domain walls in the soliton lattice. This is the first observation in the quantum Hall state that a resistance peak is induced not by the crossing of two Landau levels, but possibly by a number of pseudospin domains, i.e., interlayer phase twists.(2) : We examine an anisotropic transport in a bilayer system around the quantum Hall state at the total Landau level filling factor v=1. We find that the anisotropy becomes remarkable at the phase transition point between the commensurate and incommensurate states. This results that a unidirectional state appears around the transition.