Landau Velocity for Collective Quantum Hall Breakdown in Bilayer Graphene*

Breakdown of the integer quantum Hall effect (QHE) is associated with an electric field approaching the inter-Landau-level (LL) Zener field, ratio of the Landau gap and the cyclotron radius. The intrinsic Zener limit, corresponding to critical drift velocity, is reported here [1] using high-mobility bilayer graphene and high-frequency shot noise [2] over a large number of LLs. The steep onset of shot noise at breakdown, exhibiting super-Poissonian Fano factors, shows that collective excitations arising from electron-electron interactions are essential. The breakdown mechanism can be described by a Landau critical velocity limited by the excitation of large momentum magneto-excitons, in analogy with the roton mechanism of superfluids [3]. The fractional QHE counterpart would involve magneto-rotons [4].

[1] W. Yang, H. Graef et al., Phys. Rev. Lett. 121, 136804 (2018)
[2] W. Yang et al., Nature Nanotech. 13, 47-52 (2018)
[3] L. Landau, Phys. Rev. 60, 356 (1941)
[4] S.M. Girvin, A.H. MacDonald and P.M. Platzman, Phys. Rev. B 33, 2481 (1986)