Computers use massive amounts of energy worldwide and with the increasing dependence on computers in our life the energy utilization is only going to go up. To give you an idea, the International Energy Agency estimates that 1% of all global electricity is used by data centers. There are multiple efforts ongoing to reduce the power consumption and the recent advances by Mazhar Ali from Delft University of Technology in the Netherlands and his colleagues are a great step forward in this direction.
Mazhar and team have successfully demonstrated a working superconducting diode by sandwiching a 2D layer of a material called niobium-3 bromine-8, which is thought to have a built-in electric field, between two 2D superconducting layers. When electrons travel through the structure in one direction, they don’t encounter resistance, but in the other direction they do. This is unique because till now we had only gotten a diode working with non-superconducting metals (as they would not give any resistance in either direction).
The superconducting analogue to the semiconducting diode, the Josephson diode, has long been sought with multiple avenues to realization being proposed by theorists1,2,3. Showing magnetic-field-free, single-directional superconductivity with Josephson coupling, it would serve as the building block for next-generation superconducting circuit technology. Here we realized the Josephson diode by fabricating an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. We demonstrate that even without a magnetic field, the junction can be superconducting with a positive current while being resistive with a negative current. The ΔIc behaviour (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proved through the Fraunhofer pattern. Also, stable half-wave rectification of a square-wave excitation was achieved with a very low switching current density, high rectification ratio and high robustness. This non-reciprocal behaviour strongly violates the known Josephson relations and opens the door to discover new mechanisms and physical phenomena through integration of quantum materials with Josephson junctions, and provides new avenues for superconducting quantum devices.
The next step is to create a superconducting transistor, but there are multiple challenges ahead that need to be overcome before this can be commercially released. The first problem is that the diode only works when it’s temperature is at 2 kelvin, or -271°C which uses more energy than the diode saves. So the team is looking at alternative materials so that they can get it to work at 77 Kelvin (which is when nitrogen is liquid) so the energy used would be less and we would have an energy-saving diode.
Another issue to be sorted is that the current process of making the diode is manual and would need to be automated for large scale production. But that is a future problem as they first need to find a combination of materials that works at a reasonable energy cost.
Source: First one-way superconductor could slash energy used by computers
Paper: The field-free Josephson diode in a van der Waals heterostructure
– Suramya