Graphene brings quantum effects to electronic circuits

Two-dimensional materials bring quantum-mechanical effects into the macroscopic world, creating the potential for electronic devices which dissipate very little energy

Sense and superfluidity

At the atomic and molecular scales, the world can be a very strange place, with everyday notions of temperature, energy and physical coherence thrown into disarray. With reality at the quantum level we must talk of statistical likelihood and probability rather than simple billiard ball cause and effect.

Take the concept of superfluidity, an ultra-cold state in which matter acts as a fluid with zero viscosity. You can think of superfluidity as a generalised thermodynamic analogue of the more commonly understood electrical superconductivity, whereby electrons move through materials without resistance and energy loss.

Bose-Einstein condensation in graphene

Superfluidity was first discovered in liquid helium, at temperatures of just a few degrees above absolute zero, but the phenomenon is evident at scales ranging from the atomic to the cosmic. It is related to the state of matter known as a Bose-Einstein condensate, in which a large fraction of the particles in bulk matter occupy the lowest quantum energy state. The particles, which at higher temperatures move around in a random, haphazard fashion, can in this way behave as a coherent or at least quasi-coherent whole, thus bringing quantum-mechanical effects into macroscopic visibility.

Fascinating if somewhat esoteric physics it may be, but there is a practical side to superfluidity and Bose-Einstein condensation. For one thing it has implications for the behaviour of electronic devices, albeit specialist ones operating at ultra-low temperatures. To this end a group of researchers associated with Europe’s Graphene Flagship have investigated the properties of electrons moving in two-dimensional structures formed from graphene and gallium arsenide.

Graphene and Coulomb drag

Graphene is crystalline carbon arranged in transparent, single atom-thick layers, with the carbon atoms set in a honeycomb-like lattice. The best known of the hundreds of two-dimensional materials discovered to date, graphene has a number of unique electrical, mechanical and other properties that give it huge potential for applications ranging from electronics to super-strong structures.

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