Title: Predominance of electron-phonon scattering in the room-temperature quantum Hall effect in graphene
Author: Enrique Diez - Nanolab-Grupo de Nanotecnología. Universidad de Salamanca
When: May, 24 at 12PM (Wednesday)
Where: Sala de Seminarios, 182, ICMM
Abstract: The quantum Hall effect (QHE), a paradigmatic phenomenon of two-dimensional (2D) electron systems in high magnetic fields, typically occurs only at very low temperatures of a few Kelvin. In these conditions, lattice vibrations (so-called phonons) are suppressed and thus play a marginal role in the electrical transport. Graphene, the purely 2D form of carbon, stands out from its 2D peers due to a giant energy gap between its first two Landau levels (LLs), which enables the observation of quantum Hall states up to room temperature (RT, ~300 K). Indeed, already more than 15 years ago, high magnetic fields crucially contributed to the first observation of this RT-QHE in graphene. However, only samples resting on SiO2 had been studied in this regime, potentially missing out intrinsic physics due to detrimental substrate-induced disorder. We have investigated a collection of high-quality graphene samples encapsulated in hexagonal boron nitride (hBN) fabricated at Salamanca University. At B = 0, the RT conductivity of these van der Waals sandwiches is known to be chiefly limited by electron-phonon scattering. What happens if one applies a magnetic field strong enough to realize the RT-QHE?
