The Road to Ambient Superconductivity

The first discovery of superconductivity is credited to the Dutch physicist Heike Kamerlingh Onnes in 1911. During his experiments to investigate the properties of materials at extremely low temperatures, Onnes observed that the electrical resistance of mercury dropped suddenly and dramatically as it approached the temperature of 4.2 Kelvin (-268.95°C). Upon further experimentation and verification, Onnes confirmed that he had indeed discovered a new physical state of matter. After such an outstanding discovery, subsequent experiments were done, leading to the discovery of new materials (at this time known as conventional superconductors) as well as the fundamental properties of the superconducting state.

It was until 1957, where the first comprehensive theoretical explanation of conventional superconductivity came with the development of the BCS theory by John Bardeen, Leon Cooper, and Robert Schrieffer. This theory provided a detailed understanding of how electrons form pairs (Cooper pairs) and move through the superconducting material without resistance at temperatures below the critical temperature (the temperature at which a material becomes superconductor). The successful combination of experimental discoveries and theoretical frameworks like BCS theory laid the foundation for the field of superconductivity and opened avenues for further research and technological applications.

In 1986, Johannes Georg Bednorz and Karl Alexander Müller discovered the cuprates, a family of copper-based ceramic materials exhibiting superconducting properties at unexpectedly high temperatures, up to around 138 Kelvin (-135°C).  This discovery was considered revolutionary as it demonstrated that superconductivity could exist at higher temperatures, in contrast to conventional superconductors, which required extremely low temperatures (below 30 Kelvin) to exhibit superconducting properties. The critical temperature of the new cuprate superconductor (LaBaCuO) was around 35 Kelvin (-238.15°C), which was much higher than any known superconductor at the time.

Following this discovery, other researchers quickly confirmed and expanded upon the findings, leading to the identification of various high-temperature superconducting materials with cooper oxide composition (XY-CuO) and critical temperatures well above the boiling point of liquid nitrogen (-196°C or 77 Kelvin).

Unlike conventional superconductors, for which the BCS theory provides a comprehensive explanation, the mechanism governing un-conventional high-temperature superconductivity remains an active area of research. Scientists have proposed various theoretical models, but a consensus has yet to emerge. In the absence of a widely accepted theoretical framework, many different approaches have emerged on how to fabricate new superconductors that work at higher temperatures.

In recent years, a new family of conventional superconducting materials was discovered. Hydrogen-based superconductors are a class of materials that exhibit superconductivity at relatively high temperatures (up to 260 K) under high pressures. These materials are formed by combining hydrogen with other elements, such as sulfur, Lanthanum, Yttrium, or nitrogen, to create complex structures known as metal-hydrides. The high-pressure conditions are typically achieved using diamond anvil cells or other specialized equipment. The experimental discovery of metal-hydride superconductors has been significant because they have shown that the synergy between theory and experiment has been successful since many of these new superconductors have been predicted before experimentally being synthesized. Moreover, it has disproved the notion that conventional superconductors cannot function as high-temperature superconductors.  For instance, some hydride superconductors have critical temperatures above 260 Kelvin (-13.15°C).

High pressure can have a significant impact on superconductivity, especially in materials like hydrides and unconventional superconductors. One of the most notable effects of high pressure on superconductivity is the increase in critical temperature (Tc). In conventional superconductors, such as metals and alloys, applying high pressure can lead to an enhancement of Tc, pushing it to higher temperatures. In the case of certain materials like hydrogen-rich compounds (hydrides), high pressure can induce superconductivity at much higher temperatures than previously known. For example, hydrogen sulfide (H2S) was found to exhibit superconductivity at temperatures above 203 Kelvin (-70°C) under high pressures, representing a significant breakthrough in high-temperature superconductivity research.

High pressure plays a crucial role in investigating and understanding superconductivity, offering a means to explore new superconducting phases, enhance critical temperatures, and uncover fundamental physics governing superconducting behaviors in diverse materials.

Unearthly Materials aims to commercialize materials displaying room-temperature and ambient pressure superconductivity. Recent discoveries, backed by theoretical predictions, indicate that rare earth hydride materials under pressure are likely to exhibit room-temperature superconductivity. Utilizing our well-established expertise in high-pressure physics and hydride materials, we are making significant strides in understanding the fundamental physics of high-temperature superconductivity and developing novel materials and fabrication techniques. Advanced characterization tools have provided unprecedented insights into the electronic structure of these materials, shedding light on their exotic properties. AI models can help us make predictions for which materials may superconduct closer to ambient temperature and pressure. Aided by these developments, commercially viable near-ambient-conditions superconductors are finally within reach.

Our goal is to integrate superconductors into everyday life by introducing the world's first commercially available ambient-condition superconductor. This advancement promises to revolutionize our capabilities in addressing critical challenges in renewable energy, electronics, and transportation.