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Open Access Publications from the University of California

Topological kink plasmons on magnetic-domain boundaries.

  • Author(s): Jin, Dafei;
  • Xia, Yang;
  • Christensen, Thomas;
  • Freeman, Matthew;
  • Wang, Siqi;
  • Fong, King Yan;
  • Gardner, Geoffrey C;
  • Fallahi, Saeed;
  • Hu, Qing;
  • Wang, Yuan;
  • Engel, Lloyd;
  • Xiao, Zhi-Li;
  • Manfra, Michael J;
  • Fang, Nicholas X;
  • Zhang, Xiang
  • et al.

Two-dimensional topological materials bearing time reversal-breaking magnetic fields support protected one-way edge modes. Normally, these edge modes adhere to physical edges where material properties change abruptly. However, even in homogeneous materials, topology still permits a unique form of edge modes - kink modes - residing at the domain boundaries of magnetic fields within the materials. This scenario, despite being predicted in theory, has rarely been demonstrated experimentally. Here, we report our observation of topologically-protected high-frequency kink modes - kink magnetoplasmons (KMPs) - in a GaAs/AlGaAs two-dimensional electron gas (2DEG) system. These KMPs arise at a domain boundary projected from an externally-patterned magnetic field onto a uniform 2DEG. They propagate unidirectionally along the boundary, protected by a difference of gap Chern numbers ([Formula: see text]) in the two domains. They exhibit large tunability under an applied magnetic field or gate voltage, and clear signatures of nonreciprocity even under weak-coupling to evanescent photons.

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