What is the difference between a semiconductor and a superconductor?
Semiconductors and superconductors are materials that allow the passage of electric current through them. Therefore, they are electrical conductors, but they have fundamental differences.
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The semiconductor is an electrical conductor that has a value of electrical conductivity between the values of the insulator and that of the conductor. In other words, a semiconductor has a moderate electrical conductivity and is sensitive to variations in temperature, magnetic fields, and any impurities present in the material.
In a semiconductor, the elements are crystals whose atoms are arranged in 3D with the presence of covalent bonds between each atom. Find applications in the design of diodes, transistors or integrated circuits.
There are many semiconductor materials in the form of simple crystals such as silicon, germanium, tin, selenium or even tellurium. During its design, a semiconductor can be composed of a set of various elements such as gallium arsenide containing arsenic and gallium.
A superconductor that is an electrical conductor has a greater value of electrical conductivity than the conductivity value of a conductor. Very often, a superconductor is a chemical element or a mixture of elements that becomes almost completely resistant to the passage of electricity when cooled to a certain temperature. Therefore, a superconductor allows the passage of electricity without loss of energy. This is why the electric current flowing through a superconductor is called supercurrent.
This loss of electrical resistance at a given temperature is called the critical temperature or Tc. There are type 1 and type 2 superconductors. Type 1 materials are “classic” conductors at room temperature and become superconductors when cooled below their Tc. Type 2 materials conduct little or no current at room temperature and become superconductors when the temperature drops below their Tc.
A very thin layer for a superconducting diode
Diodes are electronic elements in which electricity only needs to flow in one direction. This is the reason why manufacturers use semiconductor materials. However, the use of this type of material leads to a loss of energy. Therefore, superconductors with zero resistance are never used for their manufacture.
Researchers at the University of Technology in the Netherlands and their German colleague at the Max Planck Institute have just created for the first time a diode based on a superconducting material that allows electricity and therefore electrons to flow in one way.
They used a material that has an integrated electric field called niobium-3 bromine-8, sandwiched between two layers of a superconducting material. The set can be considered as a 2D system as long as its thickness does not exceed the atomic thickness.
The researchers realized that when a stream of electrons passes through the sandwich in one direction, there is no resistance and therefore no loss of energy. On the other hand, in the other direction, resistance is felt. This rather unexpected discovery had not been foreseen at all by scientists and researchers still do not understand the exact workings of this system!
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Energy saving and interesting practical applications
This unexpected discovery paves the way for many practical applications, especially in the data processing centers of large groups such as Google, which sometimes host hundreds or even thousands of computer servers that consume only between 10% and 20% of world electricity production. Unfortunately, a large part of this electricity is lost in the form of heat produced by the electrical resistances of the transistors that equip these servers.
The use of this new type of superconductor could allow these servers to use much less electricity as they have no resistance and therefore no heat loss. It also means that these large data storage centers could severely limit the use of refrigeration systems that also use energy. In addition to significant energy savings, the use of this one-way superconductor would allow much faster information processing than with current systems.
This diode is also the open door to great advances in the field of quantum computing. This new diode involves the Josephson effect that allows electrons to cross a space between two superconductors by tunneling effect.
Team work doesn’t stop there. Now they want to build a superconducting transistor. They have to find new materials to do so, because their current diode operates at -271 ° C and still requires too much energy to lower and maintain that temperature.
>> Read also: 15 ° C: finally a superconductor at room temperature!
Source: Wu, H., Wang, Y., Xu, Y. et al.“The Fieldless Josephson Diode in a Van der Waals Heterostructure,” Nature604, 653–656 (2022), https://doi.org/10.1038/s41586-022-04504-8