Superconductors Part 1

Alan Cai

August 4, 2023

Levitating trains; a transformed power grid; streamlined supercomputers. The possibilities to a world with practical superconductors are endless. When a team of scientists announced their discovery of one, the scientific community was shocked and skeptical.

Conductors and semiconductors are materials that allow current to flow through them. Current is a movement of charged particles between an area of high electrical potential and an area of low electrical potential. Particles that can carry electrical charge in currents are most often electrons or holes, which are quasi-particles denoting areas where electrons could exist but do not. Current flows in the opposite direction of electrons because electrons carry negative charge. In currents, electrons do not actually travel long distances themselves. Rather, they collide with other electrons to transfer energy between power sources and loads. Despite allowing current to flow through, conductors release low amounts of heat when in use due to the interactions between the positively charged nucleus and the negatively charged electrons. Although in most circuits, the resistance hindrance induced by the conductors is negligible, larger systems such as power grids, advanced computers, or MRI scanners are adversely affected by the dissipated heat.

Superconductors are conductors that are able to negate the heat energy lost in normal conductors allowing electricity to flow unobstructedly. Dutch physicist Heike Kamerlingh Onnes discovered superconductivity as a phenomenon that occurs when a conductive material is cooled to a critical point in which it suddenly loses all resistance to electricity. Cooling conductors will lead to a decrease in resistance because less molecular movement facilitates the faster flow of electrons. Superconductors form when electrons form what are known as “Cooper pairs” and abruptly lose all electrical resistance. As described by the Bardeen–Cooper–Schrieffer theory (or BCS theory), Cooper pairs are pairs of electrons which form composite bosons and are able to occupy the same quantum state as other pairs. In atoms, negatively charged electrons repel other electrons and are attracted to positive ions. According to the BCS theory, an electron in the vicinity of positively charged ions will draw the ions toward it creating a positively charged region around it. This region hence can attract another electron, forming a Cooper pair with the first electron. These interactions are known as electron-phonon interactions and form the basis for superconductivity. Electrons, like most other elementary particles, have odd half integer spins(specifically, ½). The Pauli exclusion principle dictates that multiple particles with half integer spins are unable to occupy the same quantum state. However, as aforementioned, Cooper pairs are able to bypass this rule because the boson has a total spin of one. A reduction in heat is necessary to ensure the efficacy of the electron-phonon interaction because the low energy pairing is easily dispelled by thermal energy.

The new development of superconductors which are capable of operating at room temperature is an enormous improvement if proven to be accurate. Future articles will further expound upon the subject.