Quantum spin transport in magnetic-field-engineered nano-structures

A microwave-driven double dot system is investigated as a detector for probing a magnetic field gradient. The two dots are connected to metallic leads and a source–drain current flows under microwave irradiation. The induced current as a function of the external magnetic field exhibits resonance effects that depend directly on the local field gradient and any difference in the g-factors between the dots. The properties of the dot detector with respect to temperature, interdot hopping and the magnitude of the field gradient are examined. We demonstrate that the main factor limiting sensitivity is spin relaxation and discuss the issues in applying the method to single spin detection.