Interacting multi-channel topological boundary modes in a quantum Hall valley system
arXiv:1902.02790 · doi:10.1038/s41586-019-0913-0
Abstract
Symmetry and topology play key roles in the identification of phases of matter and their properties. Both concepts are central to understanding quantum Hall ferromagnets (QHFMs), two-dimensional electronic phases with spontaneously broken spin or pseudospin symmetry whose wavefunctions also have topological properties. Domain walls between distinct broken symmetry QHFM phases are predicted to host gapless one-dimensional (1D) modes that emerge due to a topological change of the underlying electronic wavefunctions at such interfaces. Although a variety of QHFMs have been identified in different materials, probing interacting electronic modes at these domain walls has not yet been accomplished. Here we use a scanning tunneling microscope (STM) to directly visualize the spontaneous formation of boundary modes, within a sign-changing topological gap, at domain walls between different valley-polarized quantum Hall phases on the surface of bismuth. By changing the valley occupation and the corresponding number of modes at the domain wall, we can realize different regimes where the valley-polarized channels are either metallic or develop a spectroscopic gap. This behavior is a consequence of Coulomb interactions constrained by the symmetry-breaking valley flavor, which determines whether electrons in the topological modes can backscatter, making these channels a unique class of interacting Luttinger liquids.
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- A modular ultra-high vacuum millikelvin scanning tunneling microscope
- Domain wall competition in the Chern insulating regime of twisted bilayer graphene
- A robust and tunable Luttinger liquid in correlated edge of transition-metal second-order topological insulator TaPdTe
- Quantum Hall Valley Nematics
- Surface Modification and Subsequent Fermi Density Enhancement of Bi(111)
- Topology- and symmetry-protected domain wall conduction in quantum Hall nematics
- Moiré band theory for M-valley twisted transition metal dichalcogenides
- Local Probes for Quantum Hall Ferroelectrics and Nematics
- Quantum Hall valley Ferromagnets as a platform for topologically protected quantum memory
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- Charge and spin textures of Ising quantum Hall ferromagnet domain walls
- Visualizing near-coexistence of massless Dirac electrons and ultra-massive saddle point electrons
- Spontaneous Breaking of the SU(3) Flavor Symmetry in a Quantum Hall Valley Nematic