Scientists Find Use for Bose-Einstein Condensate as a Magnetometer

Previously relegated to the realm of interesting, but without application, the Bose-Einstein Condensate (BEC) is one of the more unusual states of matter. Broadly speaking, all particles can be broken down into two groups: Fermions and Bosons. (A particle in this case can be a single particle like an electron or proton, or it can be a collection of particles bound together like the nucleus of an atom.) Fermions possess a non-integer spin (some multiple of one half) and obey the Pauli Exclusion Principle preventing a collection of them from condensing into the lowest energy state. Bosons, which have integral spins, do not possess this limitation, and under the right conditions a significant portion will condense into the lowest energy state. Common examples of BECs are superfluid helium-4 and Cooper pairs in a superconductor. Also, for many years various groups have been condensing atoms, allowing them to observe effects such as interference patterns in matter waves.

As reported in Physics News Update 785, a group at the University of Heidelberg has used a BEC to measure the minute variations in the magnetic field on a material's surface. When suspended microns above a sample, the BEC distributes itself in such a way that 'the density of atoms in the BEC ... can be converted [directly] into a map of the fields at the sample surface ... The field sensitivity achieved thereby is at the level of magnetic fields of nanotesla strength ... with a spatial resolution of only 3 microns.' While other devices have better field sensitivity or spatial resolution, 'the Heidelberg device has a region of the sensitivity-vs-resolution space all to itself.' With the unprecedented level of sensitivity and resolution provided by this new type of magnetometer, we will be better able to characterize the behavior of surfaces and design better materials.

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