Remarkably strong pairing of charge carriers in bilayer antiferromagnetic Mott insulators

Ingrid Fadelli is a writer for Phys.org.

Superconductivity, the complete disappearance of electrical resistance in some solid materials, has been investigated by physicists and material scientists over the past few years. Most of the superconductivity has been observed in materials that are very cold.

Antiferromagnets are found in many of the materials that exhibit superconductivity at high temperatures.

The formation of pairs of mobile dopants in antiferromagnets is an aspect of high-temperature superconductivity that physicists are trying to understand better. The mechanism behind the strongly correlated systems has not yet been defined.

The researchers at theMCQST, Ludwig Maximilan University of Munich, ETH ZFC;rich and Harvard University have recently unveiled high-temperature pairs of mobile charge carriers in doped antiferromagnetic Mott insulators. Their paper could shed light on the formation of mobile pairs of dopants.

The next logical step was to study pairs of holes, since we had been studying the single-dopant problem in great detail before. The mutual exclusion-property of two holes in mono-layers settings is a significant obstacle for pairs.

While conducting their studies, Grusdt and his colleagues realized that bilayer materials could be ideal platforms to examine the formation and pairing of charge carriers, as in these materials the string-based pairing mechanism they observed can develop at its full strength. The team decided to study these materials because of their properties.

We quickly realized that the mechanism we predicted would lead to enhanced binding energies would be accessible to current ultracold atom systems.

The new mechanism was unveiled in a simpler regime called the "tight-binding" regime. The main idea behind this mechanism is that two pairs of bonds are broken by paying the energy needed to break them.

The researchers use a mixed-dimensional setting in which the charges from two different layers are put together. The glue required to pair two charges derives from a string of antiferromagnetic bonds.

The mobile dopants can move in a strongly correlated concert if they follow each other's paths. In effect, we revealed an intricate interplay of magnetic and kinetic energy scales, which ultimately allows a binding of energies that systematically exceed those realizable in the tight-binding regime.

The recent work by Grusdt and his colleagues shows a very strong pair mechanism that can be analyzed in a wide range of parameters. Studies in this area of physics typically rely on heavy numerical simulations.

In the short term, the most significant implication of our work is probably the experimental feasibility of our approach, which has recently led to the long-sought experimental observation of pairs in a Hubbard-like system of ultracold atoms.

In the future, the study conducted by Grusdt and his colleagues could lead to the design and fabrication of materials that exhibit superconductivity at higher temperatures. It could help to improve the understanding of the mechanism underlying high-temperature superconductivity.

We plan to use our recent results as a staging ground for further studies of hole pairs in strongly correlated quantum systems.

In their next studies, the researchers plan to study the strontium strontium strontium strontium strontium strontium strontium strontium strontium strontium strontium stron They would like to investigate if more exotic structures composed of mobile charges and strings could form in more strongly frustrated regimes of the phase diagram.

More information: Annabelle Bohrdt et al, Strong pairing in mixed-dimensional bilayer antiferromagnetic Mott insulators, Nature Physics (2022). DOI: 10.1038/s41567-022-01561-8 Journal information: Nature Physics

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