Evidence of Lifshitz transition in thermoelectric power of ultrahigh mobility bilayer graphene

Abstract

Resolving low-energy features in the density of states (DOS) holds the key to understanding wide variety of rich novel phenomena in graphene based 2D heterostructures. Lifshitz transition in bilayer graphene (BLG) arising from trigonal warping has been established theoretically and experimentally. Nevertheless, the experimental realization of its effects on the transport properties has been challenging because of its relatively low energy scale (∼ 1 meV). In this work, we demonstrate that the thermoelectric power (TEP) can be used as an effective probe to investigate fine changes in the DOS of BLG. We observe additional entropy features in the vicinity of the charge neutrality point (CNP) in gapped BLG. This apparent violation of Mott formula can be explained quantitatively by considering the effects of trigonal warping, thereby serving as a possible evidence of a Lifshitz transition.

Graphene disk in a solenoid magnetic potential: Aharonov-Bohm effect without a two-slit-like setup

“…In real system, several factors may break the cylindrical symmetry, resulting in the mode mixing. In particular, both the spatial corrugations of a graphene sheet and charge-donating impurities placed in the substrate lead to the charge density fluctuations (i.e., p-n puddles) [15,[30][31][32]. For best existing devices, carrier density fluctuations are δn < 10 11 cm 2 near the neutrality point, corresponding to the electrostatic potential fluctuation of the order of δU ∼ 10 meV.…”

Role of the Lifshitz topological transitions in the thermodynamic properties of graphene

“…In ref. 31, experimental evidence was obtained of the Lifshitz transition in the thermoelectric power of ultrahigh mobility bilayer graphene. Resolving lowenergy features in the density of states (DOS) holds the key to understanding a wide variety of rich and novel phenomena in graphene based on 2D heterostructures.…”

“…Resolving lowenergy features in the density of states (DOS) holds the key to understanding a wide variety of rich and novel phenomena in graphene based on 2D heterostructures. The Lifshitz transition in bilayer graphene (BLG) arising from trigonal warping has been established in 31 theoretically and experimentally.…”