superconductivity

History

Superconductivity was discovered by Heike Kamerlingh Onnes in 1911, by cooling mercury to the temperature of liquid helium. Later, in 1933, the Meissner effect was discovered, and in 1957, Bardeen, Cooper, and Schrieffer developed the BCS theory, explaining the mechanism through phonon exchange.

How it works

At ultra-low temperatures, electrons, which repel each other, find a way to attract through deformation of the crystal lattice—as if two balls on a spring mattress were drawn together, indenting it. Cooper pairs form, condense into a single quantum state, and flow without resistance.

History

Superconductivity was discovered by Heike Kamerlingh Onnes in 1911, by cooling mercury to the temperature of liquid helium. Later, in 1933, the Meissner effect was discovered, and in 1957, Bardeen, Cooper, and Schrieffer developed the BCS theory, explaining the mechanism through phonon exchange.

How it works

At ultra-low temperatures, electrons, which repel each other, find a way to attract through deformation of the crystal lattice—as if two balls on a spring mattress were drawn together, indenting it. Cooper pairs form, condense into a single quantum state, and flow without resistance.

History

The discovery of superconductivity occurred in 1911, when Heike Kamerlingh Onnes measured the disappearance of resistance in mercury at 4.2 K. In 1933, Walther Meissner and Robert Ochsenfeld discovered that a superconductor expels a magnetic field. The Ginzburg–Landau theory (1950) phenomenologically described superconductivity based on an order parameter. The microscopic BCS theory (1957) explained electron pairing via phonons. In 1986, Georg Bednorz and Alex Müller discovered high-temperature superconductivity in ceramics, giving rise to a new class of materials.

How it works

The key principle is the formation of Cooper pairs and their Bose condensation. Electrons with opposite spins and momenta attract through virtual phonon exchange, overcoming Coulomb repulsion. The condensate wave function is described by a macroscopic order parameter, and its coherence leads to supercurrent. The BCS theory provides an expression for the critical temperature, where the Debye frequency and electron-phonon coupling potential are important. The electrodynamics of superconductors is described by the London equations, which explain the Meissner effect and perfect conductivity by linking supercurrent to fields. Superconductivity is a macroscopic manifestation of quantum mechanics, where the Schrödinger equation for the Cooper pair condensate describes a single wave function.

Open problems & fun facts

The mechanism of high-temperature superconductivity in cuprates remains unresolved; Search for materials with superconductivity at room temperature and atmospheric pressure; Theoretical prediction of Tc for new superconductors; Understanding the pseudogap phase in underdoped cuprates; Practical application: creating stable flexible superconducting cables and devices on large scales

💡 Magnetic levitation of superconductors over magnets is not just a trick: the superconductor is firmly "suspended" in the air due to the effect of quantum flux pinning.