David C. Dillen | Searcharxiv

arXiv2016

Giant Frictional Drag in Double Bilayer Graphene Heterostructures

We study the frictional drag between carriers in two bilayer graphene flakes separated by a 2 $-$ 5 nm thick hexagonal boron nitride dielectric. At temperatures ($T$) lower than $\sim$ 10 K, we observe a large anomalous negative drag emerging predominantly near the drag layer charge neutrality. The anomalous drag resistivity increases dramatically with reducing {\it T}, and becomes comparable to the layer resistivity at the lowest {\it T} = 1.5 K. At low $T$ the drag resistivity exhibits a breakdown of layer reciprocity. A comparison of the drag resistivity and the drag layer Peltier coefficient suggests a thermoelectric origin of this anomalous drag.

cond-mat.mes-hall↗

arXiv2014

Chemical Potential and Quantum Hall Ferromagnetism in Bilayer Graphene

Bilayer graphene has a unique electronic structure influenced by a complex interplay between various degrees of freedom. We probe its chemical potential using double bilayer graphene heterostructures, separated by a hexagonal boron nitride dielectric. The chemical potential has a non-linear carrier density dependence, and bears signatures of electron-electron interactions. The data allow a direct measurement of the electric field-induced bandgap at zero magnetic field, the orbital Landau level (LLs) energies, and the broken symmetry quantum Hall state gaps at high magnetic fields. We observe spin-to-valley polarized transitions for all half-filled LLs, as well as emerging phases at filling factors ν= 0 and ν= +-2. Furthermore, the data reveal interaction-driven negative compressibility and electron-hole asymmetry in N = 0, 1 LLs.

cond-mat.mes-hall↗