Quantum Detection using Magnetic Avalanches in Single-Molecule Magnets

Single-molecule magnets are high spin molecules that are highly isolated from each other so that they essentially act as single non-interacting magnets at the molecular level. They have a doubly degenerate magnetic ground state which forms a metastable state in the presence of an external magnetic field. At low temperatures (<2K for Mn-12-ac), this state is stable on a timescale of months. A small deposition of localized energy can break this metastable state and release the stored Zeeman energy in the molecule. This release in energy quickly causes neighboring molecules to relax and repeat the process throughout the whole crystal, causing what is known as a magnetic avalanche. The effect can easily be measured with a hall sensor or SQUID and makes it possible to detect small energy deposits (theorized to meV). I will present research where we successfully detected magnetic avalanches in Mn-12-ac caused by incoming alpha particles; the first in this new generation of detector technology.