Recent advances in the mechanical detection of magnetic resonance have led to the sensitive measurement of single electron spins and small ensembles of nuclear spins in the solid-state.  In 2009, the technique was used to make a three-dimensional (3D) magnetic resonance image (MRI) of a single virus particle with resolution better than 10 nm.  This technique proved itself to be 100 million times more sensitive than conventional inductively-detected MRI.  Despite this and other results – including the detection of a single electron spin by mechanical means in 2004 – mechanical detection of magnetic resonance has not yet been widely applied to technologically relevant solid-state nanostructures.

With this research project, we propose to investigate solid-state nanostructures such as semiconductor quantum dots (QDs), nanowires, nanotubes, and nitrogen-vacancy (NV) centers using the techniques of mechanically-detected magnetic resonance.  In short, we propose to magnetically couple ultra-sensitive cantilevers to small ensembles of electron and nuclear spins within semiconductor nanostructures.  We then aim to exploit this coupling to do such tasks as nanometer-scale, sub-surface MRI of semiconductor nanostructures; the measurement and manipulation of single electron spins; and the achievement of strong coupling between a single solid-state spin and a mechanical oscillator.

During the last decade or so, we have witnessed the rapid development of mesoscopic devices able to controllably trap single electrons.  Some examples include QDs, single electron transistors (SETs), nanotubes, and NV centers.  These devices typically contain on the order of 10 to 100 thousand nuclei, which can interact with the trapped electrons via spin-spin coupling.  A flourishing community of researchers exists that study the physics of these devices using measurements of electrical transport or measurements of optical emission and absorption.  Due to the small ensembles of spins involved and the tiny total magnetic moments, there are very few measurements of magnetic resonance in such systems using purely magnetic couplings.  Conventional MRI techniques are simply not sensitive enough for such small samples.  Therefore, studies of spin in solid-state nanostructures have been limited to the small subset of systems which are accessible by either electrical or optical means.  Our proposal aims to develop a relatively general technique to do magnetic resonance in semiconductor nanostructures.  The potential benefits include nanometer-scale 3D imaging of sub-surface nanostructures and the measurement and manipulation of electrically and optically inaccessible single spins.