Kumar Ravi, Srivastav Saurabh Kumar, Spånslätt Christian, Watanabe K, Taniguchi T, Gefen Yuval, Mirlin Alexander D, Das Anindya
Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, S-412 96, Göteborg, Sweden.
Nat Commun. 2022 Jan 11;13(1):213. doi: 10.1038/s41467-021-27805-4.
The presence of "upstream" modes, moving against the direction of charge current flow in the fractional quantum Hall (FQH) phases, is critical for the emergence of renormalized modes with exotic quantum statistics. Detection of excess noise at the edge is a smoking gun for the presence of upstream modes. Here, we report noise measurements at the edges of FQH states realized in dual graphite-gated bilayer graphene devices. A noiseless dc current is injected at one of the edge contacts, and the noise generated at contacts at length, L = 4 μm and 10 μm away along the upstream direction is studied. For integer and particle-like FQH states, no detectable noise is measured. By contrast, for "hole-conjugate" FQH states, we detect a strong noise proportional to the injected current, unambiguously proving the existence of upstream modes. The noise magnitude remains independent of length, which matches our theoretical analysis demonstrating the ballistic nature of upstream energy transport, quite distinct from the diffusive propagation reported earlier in GaAs-based systems.
在分数量子霍尔（FQH）相中，“上游”模式的存在与电荷电流流动方向相反，这对于具有奇异量子统计的重整化模式的出现至关重要。边缘处过量噪声的检测是上游模式存在的确凿证据。在此，我们报告了在双石墨门控双层石墨烯器件中实现的FQH态边缘的噪声测量。在一个边缘接触处注入无噪声直流电流，并研究沿上游方向距离L = 4μm和10μm处接触点产生的噪声。对于整数和类粒子FQH态，未测量到可检测到的噪声。相比之下，对于“空穴共轭”FQH态，我们检测到与注入电流成比例的强噪声，明确证明了上游模式的存在。噪声幅度与长度无关，这与我们的理论分析相符，该分析表明上游能量传输具有弹道性质，与早期基于砷化镓系统中报道的扩散传播截然不同。
