In the vast majority of superconducting materials, Cooper pairs have what is known as even parity, which essentially means that their wave function does not change when electrons swap spatial coordinates. Conversely, some unconventional superconductors have been found to contain odd-parity Cooper pairs. This quality makes these unconventional materials particularly promising for quantum computing applications.

Past studies have predicted that noncentrosymmetric superconductors, which have a crystal structure with no center of inversion, could exhibit unique and unusual properties. In recent years, noncentrosymmetric superconductors have become a popular topic of research due to the structure of the Cooper pairs contained within them, which have a mixture of odd and even parity.

CaPtAs is a new noncentrosymmetric superconductor discovered by researchers at Zhejiang University. Together with scientists at the Paul Scherrer Institut and other institutes worldwide, these researchers have recently carried out a study investigating unconventional superconductivity in this compound. Their paper, published in Physical Review Letters, offers evidence that in its superconducting state, CaPtAs simultaneously exhibits both nodal superconductivity and broken time-reversal symmetry (TRS).

An exotic physical phenomenon known as a Kohn anomaly has been found for the first time in an unexpected type of material by researchers at MIT and elsewhere. They say the finding could provide new insights into certain fundamental processes that help determine why metals and other materials display the complex electronic properties that underlie much of today’s technology.

The way electrons interact with phonons—which are essentially vibrations passing through a crystalline material —determines the physical processes that take place inside many electronic devices. These interactions affect the way metals resist electric current, the temperature at which some materials suddenly become superconductors, and the very low temperature requirements for quantum computers, among many other processes.

But electron-phonon interactions have been difficult to study in detail because they are generally very weak. The new study has found a new, stronger kind of unusual electron-phonon interaction: The researchers induced a Kohn anomaly, which was previously thought to exist only in metals, in an exotic material called a topological Weyl semimetal. The finding could help shed light on important aspects of the complex interplay between electrons and phonons, they say.

To create large quantum networks, researchers will first need to develop efficient quantum repeaters. A key component of these repeaters are quantum memories, which are the quantum-mechanical equivalents of more conventional computer memories, such as random-access memories (RAM).

Ideally, a quantum memory should be able to retain information for substantial periods of time, store true quantum states, read out data efficiently and operate at low-loss telecommunication wavelengths. While research teams have made great progress in the development of quantum memories, no solution proposed so far has been able to meet all of these requirements simultaneously.

With this in mind, researchers at Delft University of Technology (TU Delft) set out to develop a new mechanical quantum memory with sufficiently long storage times, a high readout efficiency, and the ability to operate at telecom wavelengths. The memory they devised, presented in a paper published in Nature Physics, could ultimately enable the practical implementation of mechanical systems with quantum effects developed in their previous works.