Inducing Superconducting Correlation in Quantum Hall Edge States
Figure 4: Exponential width dependence on negative response at B = 8 T and ν = 2.*
[Reprinted by permission from Macmillan Publishers Ltd: Nature Physics ©2017]
The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a two-dimensional system. A superconductor (SC) contacting these states can provide correlations of the quasiparticles in the dissipationless edge states. In a new study led by Prof. Philip Kim, researchers fabricated highly transparent and nanometre-scale SC junctions to graphene. The study demonstrated that the QH edge states can couple via superconducting correlations through the SC electrode narrower than the superconducting coherence length. Writing in a recent issue of Nature Physics, the physicists observe that the chemical potential of the edge state exhibits a sign reversal across the SC electrode. This provides direct evidence of conversion of the incoming electron to the outgoing hole along the chiral edge state, termed crossed Andreev conversion (CAC). The authors show that CAC can successfully describe the temperature, bias and SC electrode width dependences. This hybrid SC/QH system could provide a novel route to create isolated non-Abelian anyonic zero modes, in resonance with the chiral edge states. Prof. Amir Yacoby and colleagues from MIT and National Institute for Materials Science, Tsukuba, Japan, also contributed to the study.
* See Gil-Ho Lee, Ko-Fan Huang, Dmitri K. Efetov, Di S. Wei, Sean Hart, Takashi Taniguchi, Kenji Watanabe, Amir Yacoby & Philip Kim, "Inducing superconducting correlation in quantum Hall edge states," Nature Physics (2017) doi:10.1038/nphys4084.