Is magic-angle graphene a topological heavy-fermion system? · revision history
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- Title
- Is magic-angle graphene a topological heavy-fermion system
- Plain
- One theory describes the flat-band electrons of magic-angle graphene as magnetic moments localized at particular spots of the moire pattern, mixed with fast conduction electrons as in heavy-fermion metals, and whether experiments confirm this picture is debated.
- Precise
- Song and Bernevig (PRL 129, 047601, 2022, arXiv:2111.05865) mapped the continuum model of magic-angle twisted bilayer graphene onto localized f-orbitals at AA-stacked regions hybridized with topological dispersive c-electrons. Determine whether experiments at $\nu = 0\ \text{to}\ \pm 3$ show the defining features of this picture: Curie-like local-moment susceptibility and moment entropy of order $k_B \operatorname{ln} 2$ per moire cell at $T \sim 10\,\mathrm{K}$, a coherence temperature below which the moments are screened, and a hybridization gap or Kondo-like resonance in tunnelling at AA sites. An answer is yes or no, based on measured coherence temperature, moment entropy and spectral weight compared with the model parameters.
- Settled by
- Tunnelling spectroscopy resolving a temperature-dependent hybridization feature at AA sites, together with thermodynamic measurement of the moment entropy and its quenching below a coherence temperature.
- Kind
- phenomenon
- Answer type
- yes-no
- References
- (empty)
- Literature status
- contested
- Status note
- Large magnetic entropy consistent with fluctuating moments was reported in 2021, but whether a Kondo coherence scale exists is debated as of 2026, to this survey's knowledge.
- Posed since
- 2021