niobium · film
Nb
Elemental niobium, which has the highest transition temperature of any element at ambient pressure, and the material most superconducting circuits are wired in.
Nb in numbers
- Transition temperature
- 9.3 K
- Made as
- film
- Nitrogen line
- Below 77 K
What Nb runs in today
Transmon circuit wiring and resonators; accelerator RF cavities.
Source: Textbook value; the transmon literature from Koch et al. (2007) onward
Why engineers choose Nb
Niobium is what a superconducting circuit is made of everywhere the circuit is not the junction. It patterns cleanly. It survives the process temperatures a fab wants to use. Its surface can be prepared to the point where a resonator holds energy for a very long time. And it is a single element, so there is no stoichiometry to hold constant across a wafer. The same properties put it inside accelerator cavities, where the figure of merit is how little of the drive power the wall absorbs.
Where Nb stops
Niobium still needs a helium bath or a dilution refrigerator, which is acceptable for the machines that use it and disqualifying for everything else. Niobium is not a candidate for anything that has to leave a laboratory.
Fields built on Nb
- Quantum computersMost of the largest processors are superconducting circuits, held near absolute zero.
- Biomagnetic sensingSQUIDs read the magnetic field of brain activity through the skull.
- Superconducting logicSwitching at a fraction of the energy of silicon. Demonstrated for decades, never volume-made.
- Particle accelerators1,232 superconducting dipoles bend the beam around 27 km at CERN.
Nb and the other film conductors
Terms used on this page about Nb
SuperMatics is a platform infrastructure company for superconducting devices: software that finds the material and the process, lab work that makes and measures it, and pilot manufacturing with industrial partners.If a conductor on this page stops short of what your device needs, tell us about it.