Localization to delocalization probed by magnetotransport of hBN/graphene/hBN stacks in the ultra-clean regime

Abstract

We report on magnetotransport in a high-quality graphene device, which is based on monolayer graphene (Gr) encapsulated by hexagonal boron nitride (hBN) layers, i.e., hBN/Gr/hBN stacks. In the vicinity of the Dirac point, a negative magnetoconductance is observed for high temperatures > ~ 40 K, whereas it becomes positive for low temperatures ≤ ~ 40 K, which implies an interplay of quantum interferences in Dirac materials. The elastic scattering mechanism in hBN/Gr/hBN stacks contrasts with that of conventional graphene on SiO2, and our ultra-clean graphene device shows nonzero magnetoconductance for high temperatures of up to 300 K.

Effect of Boundary Scattering on Magneto-Transport Performance in BN-Encapsulated Graphene

“…As the temperature increases, the magnitude of negative MR decreases monotonically and the side peak at 𝐵max weakens. Nevertheless, in contrast to the WL effect that normally appears at relatively low temperatures,[19][20][21] the boundary-scatteringdominated negative MR effect observed here is quite robust, persisting even at temperatures of up to 300 K at high doping levels (𝑛 = 3.9 × 10 12 cm −2 at 𝑉BG = 50 V). Noticeably, for low 𝑛 cases with smaller negative MR at the base temperature (see Fig.3(b) for 𝑛 = 1.1 × 10 12 cm −2 at 𝑉BG = 10 V), thermally induced suppression is more evident, manifested as a classical positive MR at elevated temperatures.…”