Energy dissipation on quantum systems and 2D materials

Understanding the nanoscale energy dissipation is nowadays among few priorities particularly in solid state systems. Breakdown of topological protection, loss of quantum information and disorder-assisted hot electrons scattering in graphene are few examples, where the presence of energy dissipation has a great impact on the studied object. It is therefore critical to know, how and where the energy leaks.
The aim of this project is to address this issue by using a highly sensitive pendulum geometry Atomic Force Microscope (p-AFM), oscillating like a tiny pendulum over the sample surface. The microscope is perfectly suited to measure tiny amounts of dissipation, the tip position is controlled with atomic accuracy owing to a tunnelling current and the enhanced sensitivity allows to distinguish between electronic, phononic or van der Waals type of dissipation. The measurements can be performed in a wide range of temperatures from T=5K to room temperature and in magnetic fields spanning from B=0T to B= ± 7T. The design of the sample holder allows to perform dissipation measurements while passing electric current in the plane as well as to apply in-plane voltage to the the sample surface as well as adding two contact wires.
The experiments showed that the mechanical oscillations of the cantilever and the sample surface can sense the quantum effects of 2D materials or quantum systems. Indeed, quantum dot-like behaviour is reported on free-standing graphene monolayer where electrons charging and discharging events are observed and dissipation maps show Coulomb rings. In addition to that, the band filling of twisted bilayer graphene at the magic angle twist and a signature of potential orbital ferromagnetic behaviour for the band filling equal to 3ns/4 was investigated. Last, the transition between ferromagnetic to paramagnetic phase in a molybdenum disulfate monolayer was investigated and revealed a linear dependence of the magnetic susceptibility as suggested by theoretical studies.