Quantum Capacitance of a Topological Insulator-Ferromagnet Interface

Abstract

We study the quantum capacitance in a topological insulator thin film system magnetized in the in-plane direction in the presence of an out-of-plane magnetic field and hexagonal warping. To first order, the modification in quantum capacitance due to hexagonal warping compared to the clean case, where both the in-plane magnetization and hexagonal warping are absent, is always negative, and increases in magnitude monotonically with the energy difference from the charge neutrality point. In contrast, the change in the quantum capacitance due to in-plane magnetization oscillates with the energy in general, except when a certain relation between the inter-surface coupling, out of plane Zeeman energy splitting and magnetic field strength is satisfied. In this special case, the quantum capacitance remains unchanged by the in-plane magnetization for all energies.

Steep-slope transistors enabled with 2D quantum coupling stacks

“…Recently, negative quantum capacitance (NQC) induced by 2D electron gas (2DEG) has been proposed to achieve low SS [24][25][26][27][28][29][30]. NQC was observed in graphene at a strong magnetic field [25].…”

“…Negative electronic compressibility and quantum capacitance can be achieved even without the presence of a magnetic field, by tuning the Fermi energy near the Dirac point [27]. NQC was also observed in topological insulators [28][29][30]. The gate-channel stacks consisting of these quantum materials have strong electron-electron interaction which significantly enhances NQC and leads to small SS [31,32].…”

Probing the anisotropy of Landau levels in phosphorene by magneto-capacitance with a parabolic potential confinement

“…In return, probing the quantum oscillations from MC is a reliable method to detect the LLs of a 2D electron system. And it has been successfully used to characterize the LLs of graphene [45] and topological insulators [40,41,48,49] as well as the subbands of BP thin films [46].…”