Quantum instrument to measure the faintest magnetic fields

a) A conventional superconducting quantum interference device (SQUID) consists of a superconducting ring interrupted at two points by weak links (in this case a graphene layer). b) The new SQUID is made up of a stack of two-dimensional materials, including two graphene layers separated by a thin film of boron nitride. (University of Basel, Department of Physics)

Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields. At the heart of the superconducting quantum interference device are two atomically thin layers of graphene, which the researchers combined with boron nitride. Instruments like this one have applications in areas such as medicine, besides being used to research new materials.

To measure very small magnetic fields, researchers often use superconducting quantum interference devices, or SQUIDs. In medicine, their uses include monitoring brain or heart activity, for example, while in the earth sciences researchers use SQUIDs to characterize the composition of rocks or detect groundwater flows. The devices also have a broad range of uses in other applied fields and basic research.

The team at the University of Basel’s Department of Physics and the Swiss Nanoscience Institute has now succeeded in creating one of the smallest SQUIDs ever built.

The tiny device for measuring magnetic fields is only around 10 nanometers high – roughly a thousandth of the thickness of a human hair. The instrument can trigger supercurrents that flow in minuscule spaces. Moreover, its sensitivity can be adjusted by changing the distance between the graphene layers. With the help of electrical fields, the researchers are also able to increase the signal strength, further enhancing the measurement accuracy.

The paper has been published in Nano Letters.

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