Flat bands and nontrivial topological physics are two important topics of condensed matter physics. With a unique stacking configuration analogous to the Su–Schrieffer–Heeger model, rhombohedral graphite (RG) is a potential candidate for realizing both flat bands and nontrivial topological physics. Here, we report experimental evidence of topological flat bands (TFBs) on the surface of bulk RG, which are topologically protected by bulk helical Dirac nodal lines via the bulk-boundary correspondence. Moreover, upon in situ electron doping, the surface TFBs show a splitting with exotic doping evolution, with an order-of-magnitude increase in the bandwidth of the lower split band, and pinning of the upper band near the Fermi level. These experimental observations together with Hartree–Fock calculations suggest that correlation effects are important in this system. Our results demonstrate RG as a platform for investigating the rich interplay between nontrivial band topology, correlation effects, and interaction-driven symmetry-broken states.
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Low-energy effective theory and anomalous Hall effect in monolayer $\mathrm{WTe}_2$
We develop a symmetry-based low-energy theory for monolayer \mathrm{WTe}_2 W T e 2 in its 1T ^{\prime} ′ phase, which includes eight bands (four orbitals, two spins). This modelreduces to the conventional four-band spin-degenerate Dirac model nearthe Dirac points of the material. We show that measurements of the spinsusceptibility, and of the magnitude and time dependence of theanomalous Hall conductivity induced by injected or equilibrium spinpolarization can be used to determine the magnitude and form of thespin-orbit coupling Hamiltonian, as well as the dimensionless tilt ofthe Dirac bands.
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- Award ID(s):
- 1853048
- PAR ID:
- 10326669
- Date Published:
- Journal Name:
- SciPost Physics
- Volume:
- 12
- Issue:
- 4
- ISSN:
- 2542-4653
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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