A team of researchers at Yale University has found compelling evidence for a new type of superconducting material. “The discovery also lends tangible support to a long-held theory about superconductivity — that it could be based upon electronic nematicity, a phase of matter in which particles break their rotational symmetry,” said the researchers. For context, superconductivity allows electricity to flow without any resistance or energy loss.
Electronic nematicity and superconductivity:
At high temperatures, electrons typically move freely within the material’s atomic lattice. However, as the temperature decreases, electrons in a nematic phase exhibit a preference for movement along specific directions. “In some instances, the electron may start to fluctuate between preferring one direction, then the other. This is called nematic fluctuation,” explained the press release. These fluctuations have long been theorized to play a role in inducing superconductivity. However, experimental verification of this connection has remained elusive. The Yale team, led by physicist Eduardo H. da Silva Neto, investigated iron selenide materials mixed with sulfur. “We started on a hunch that there was something interesting happening in certain iron selenide materials mixed with sulfur, relating to the relationship between superconductivity and nematic fluctuations,” said da Silva Neto.
Materials were chosen due to their unique properties
“These materials are ideal because they display nematic order and superconductivity without some of the drawbacks, such as magnetism, that can make it difficult to study them,” explained da Silva Neto. “You can detach magnetism from the equation.” To probe the relationship between nematic fluctuations and superconductivity, the researchers utilized a scanning tunneling microscope (STM). This instrument allows for the imaging of electronic behavior at the atomic level. Besides, these measurements were performed at extremely low temperatures. “For the study, the researcher’s chilled iron-based materials down to a temperature of less than 500 millikelvins over a period of several days,” read the press release. The STM measurements revealed the presence of a “superconducting gap,” a key indicator of superconductivity. The characteristics of this gap precisely matched the theoretical predictions for superconductivity driven by electronic nematicity. “This has been elusive to prove, because you have to do the challenging STM measurements at very low temperatures to be able to measure the gap accurately,” remarked da Silva Neto. This finding provides the strongest evidence to date supporting this long-standing hypothesis.
Implications of this discovery are huge
The implications of this discovery are significant. It provides a deeper understanding of the mechanisms behind superconductivity and opens new avenues for the development of novel superconducting materials. The Yale team plans to conduct further research to explore how changes in material composition affect the superconducting properties and the role of nematic fluctuations. “The next step is to look even more closely. If we keep increasing the sulfur content, what will happen with the superconductivity? Will it die? Will spin fluctuations return? Several questions come up that we will explore next,” concluded da Silva Neto. The development of new superconducting materials could lead to transformative technologies, including highly efficient power grids, advanced medical imaging devices, and high-speed computing systems.
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