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Johannes Fink and colleagues build geometric superinductor that breaks resistance quantum “limit”

NOMIS researcher Johannes Fink and his team have built a geometric superinductor that surpasses the resistance quantum “limit.”

• Physics 13, s141

A geometric superinductor made of a tightly wound aluminum wire can achieve an impedance about 5 times larger than a hypothesized fundamental limit.

Johannes Fink

A superinductor is an inductor with an electrical impedance that exceeds 6.45 kΩ, a value set by Planck’s constant and the charge of an electron. It was thought that inductors could only exceed this value—known as the resistance quantum—through a mechanism called kinetic inductance, which is the inductance from a material’s intrinsic properties. Now, Matilda Peruzzo, Andrea Trioni, and colleagues of the Institute of Science and Technology Austria show another route to high impedance by building a geometric superinductor—where the superinductance comes instead from the material’s geometric arrangement [1].

Kinetic inductance can come from several types of material properties. For example, granular aluminum can act as a kinetic inductor because grain boundaries in the material slow down—or impede—current. Geometric inductance, on the other hand, boosts impedance through the shape or pattern that a material is molded into. A coiled wire, for example, has a greater impedance than a straight wire because the magnetic field of each loop acts on other loops to raise the overall impedance.

M. Peruzzo et al. [1]

To achieve geometric superinductance, Peruzzo, Trioni, and colleagues nanofabricated very tightly wound spirals of thin aluminum wire on a silicon-based substrate. They then removed as much of the substrate as they could, creating a nearly free-standing coil. They made more than a hundred such devices with various geometries. Ultimately, they achieved impedances of up to 5 times the resistance quantum for ac currents with frequencies as high as a few gigahertz, showing unequivocally that neither the resistance quantum nor the impedance of free space—another hypothesized limit for geometric inductors—is actually a fundamental limit.

–Erika K. Carlson

Erika K. Carlson is a Corresponding Editor for Physics based in New York City.

Go to this Physics synopsis: Geometric Inductor Breaks Resistance Quantum “Limit”

Read the Physical Review Applied publication: Surpassing the Resistance Quantum with a Geometric Superinductor


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