Breakthrough in Superconductors: Scientists Discover an Invisible Phenomenon.

The discovery makes superconductivity more accessible.

Understanding the connection between spin liquids and superconductivity may lead to the creation of room-temperature-operating superconductors, which would have far-reaching implications for our daily lives.

High-speed hovertrains, magnetic resonance imaging equipment, efficient power lines, quantum computing, and other technologies could all benefit significantly from using superconductors. Superconductivity necessitates shallow temperatures. However, its application is constrained. Their complex and expensive needs make it challenging to incorporate them into current technology.

Unlike regular metallic conductors, whose electrical resistance decreases gradually as temperature is lowered, even down to near absolute zero, superconductors have a critical temperature beyond which it rapidly drops to zero.

Current efforts in superconductivity research are primarily focused on finding superconductors that do not necessitate these shallow temperatures. No one knows how these superconductors work, which is the biggest mystery in this area. More uses could be found for superconductivity if the method by which it is created at high temperatures could be better understood.

Researchers from Israel's Bar-Ilan University have made strides toward solving this enigma with their recent work published in the journal Nature. The researchers took pictures of an otherwise unseen occurrence using a magnetic microscope scanning SQUID (superconducting quantum interference device).

When high-temperature superconductors were first discovered, scientists were taken aback. Researchers expected to find materials with high superconductivity in metals. The best superconductors are, surprisingly, insulating ceramic materials.

Exploring shared characteristics across these ceramics could lead to insights into their superconductivity's origin and better regulation of the critical temperature. For example, the electrons in these materials exhibit high levels of mutual repulsion. Therefore, they are restricted in their mobility. Instead, they are imprisoned within a lattice that repeats at regular intervals.

Electric current is caused by electrons' charge traveling around, and electrons' spin is the other distinguishing feature. Electrons' magnetic characteristics can be attributed to their quantum property, spin. Each electron has the magnetic force of a small bar magnet. Standard materials have electrons with charge and spin that are "built-in" and cannot be removed.

However, a peculiar event occurs when electrons interact in certain quantum materials termed "quantum spin liquids," splitting each electron into a particle with charge (but no spin) and a particle with spin (and no charge). The existence of quantum spin liquids in high-temperature superconductors has been proposed as a possible explanation for the excellent superconductivity observed in such materials.

The difficulty arises from these spin liquids being "invisible" to the majority of currently available measurement techniques. Now, no experiment can confirm or investigate the Nature of a material's suspicion to be a spin liquid. It's hard to detect since it doesn't interact with light like dark matter.

This work is essential in creating a method to analyze spin liquids. It was undertaken by Professor Beena Kalisky and Doctoral Student Eylon Persky of the Physics Department at Bar-Ilan University, together with their collaborators. Scientists put a spin liquid in contact with a superconductor to investigate its peculiarities. They employed a synthetic material composed of superconductors and liquid spin candidate atomic layers.

In contrast to signal-free spin liquids, Superconductors have easily measurable magnetic fingerprints. As a result, "we were able to examine the properties of the spin liquid by monitoring the minor changes it created in the superconductor," as per Persky's explanation. Scientists looked at the heterostructure's characteristics using a scanning SQUID, a magnetic sensor sensitive enough to detect both magnetism and superconductivity.

We have witnessed the formation of vortices in the superconductor. These whirlpools represent swirling electric currents and hold one quantum of magnetic flux each. However, in our situation, the vortices formed independently without needing a magnetic field, as Kalisky explains. This finding demonstrated that the material itself produced a magnetic field. Unexpectedly, this field did not manifest itself in a straightforward experiment. Kalisky chimes in, "Surprisingly, we found that the material's magnetic field was invisible to a direct magnetic measurement."

The results indicated the presence of a "hidden" magnetic phase that was revealed by contact with the superconducting layer in the experiment. The researchers, who worked together from Bar-Ilan University, the Technion, the Weizmann Institute, the University of California, Berkeley, and the Georgia Institute of Technology, found that the magnetic phase was likely caused by the interaction between the liquid spin layer and the superconducting layer. The spin-charge separation in the spin liquid is responsible for the latent magnetism. Without an external "actual" magnetic field, the superconductor will respond to this magnetic field, creating vortices.

This is the first time the connection between the two states of matter has been seen directly. The features of the enigmatic spin liquids, such as the interactions between electrons, are now accessible thanks to these findings. Moreover, the results pave the way for further research into the connection between superconductivity and other electronic phases by building additional layered materials. More investigation into the relationship between spin liquids and superconductivity could lead to the development of room-temperature-operable superconductors, which would have far-reaching implications for our daily lives.