Entropy Spectroscopy of a Bilayer Graphene Quantum Dot

Abstract

Bilayer graphene (BLG) has emerged as a promising platform for hosting qubits within 2D materials. By encapsulating it in a dielectric and applying gating techniques, one can electrostatically confine individual charge carriers, both electrons and holes, and thus obtain what is called a quantum dot (QD). Charge detection schemes allow us study the quantum properties of these trapped charge carriers. In BLG, electrons and holes possess not only a spin but also a valley degree of freedom, arising from its lattice structure. Due to the nontrivial Berry curvature, the valley is subject to an energy splitting in perpendicular magnetic field, similar to spin but with a strength of one to two orders of magnitude larger. Experiments have shown that these valley states exhibit decay times of tens of seconds, contrary to tens of milliseconds for spin states. In this talk, I will introduce the basic physics and technology of BLG QDs, followed by how we can experimentally characterize the spin and valley quantum states in BLG by measuring the thermodynamic entropy of a QD, a classical state quantity