The dilemma faced by materials scientists has been broken: room temperature superconductivity has been born.

"This is the first time that we can really claim to have discovered room temperature superconductivity," said Ion Errea, a condensed matter theorist at the University of Basque Country in Spain (he was not involved in this work).

Chris Picard, a material scientist at Cambridge University, said with emotion: "This is obviously a milestone." When talking about the temperature of 15, he said: "This is equivalent to the room temperature of a slightly cool room, perhaps a Victorian cottage in England."

This new compound was developed by a research team led by Ranga Dias of the University of Rochester. While the researchers cheered these achievements, they also stressed that if the fragile quantum effect appears with superconductivity under real environmental conditions, this material will never be applied to lossless wires, frictionless high-speed trains or any revolutionary technology that may be ubiquitous in the future. This is because this substance is superconducting only when it is crushed by a pair of diamonds at room temperature, and its pressure limit is about 75% of the pressure in the core.

Piccard said: "room temperature superconductivity has always been a topic of discussion, but they may not know that we will carry out this research under such high pressure."

At present, a major challenge for materials scientists is that it is difficult to find superconductors that can work at both normal temperature and normal pressure. Some characteristics of this new compound bring hope for finding a suitable mixture in the future.

When free-flowing electrons hit the atoms that make up the metal, ordinary wires produce resistance. However, in 19 1 1 year, researchers found that at low temperature, electrons can induce vibration in the crystal lattice of metal atoms, which in turn will make electrons polymerize to form electron pairs, which are called Cooper pairs. Cooper pairs are governed by quantum rules, and they pass through the metal lattice without any obstacles. Superconducting fluid will also repel the magnetic field-this effect can make the maglev vehicle float on the superconducting track without friction.

However, when the temperature of the superconductor rises, the particles will shake randomly, breaking the fine fluctuation of electrons.

For decades, researchers have been looking for a compact Cooper-pair superconductor that can withstand daily environmental temperatures. 1968, Neil Ashcroft, a solid-state physicist at Cornell University, proposed that this can be achieved by using the lattice of hydrogen atoms. The size of hydrogen atoms is extremely small, so electrons are closer to the nodes of the lattice, thus increasing their interaction with vibration. In addition, the light weight of hydrogen atoms also makes those guided waves vibrate faster, thus further enhancing the force of bonding Cooper pairs.

The pressure required to squeeze hydrogen into the metal lattice is very high. Nevertheless, ashcroft let people see the dawn through his own work: some kind of "hydride", that is, a compound composed of hydrogen and another element, may produce superconductivity of metallic hydrogen under more easily available pressure.

In 2 1 century, more progress has been made in this field. Thanks to the simulation technology of supercomputer, theorists can predict the properties of various hydrides; The widespread use of diamond anvil helps experimenters to put pressure on the most promising candidate hydrides to test their properties.

Suddenly, hydride began to create one record after another. In 20 15, a research team in Germany found that the irritating compound hydrogen sulfide found in rotten eggs was superconducting at 70℃ and10.5 million atmospheric pressure. Four years later, lanthanum hydride was superconducting in the same laboratory at a temperature of about 23℃ and an air pressure of 6.5438+0.8 million atmospheres. The other group found evidence of superconductivity at a temperature of about 13.

Diaz Laboratory at the University of Rochester broke these records. Based on intuition and rough calculation, the research team tested a series of hydrogen compounds to find the best proportion of hydrogen. If the hydrogen content is too small, the compound cannot have stable superconductivity like hydrogen. If too much is added, this compound will be like hydrogen, and metallization can only be achieved when a pressure sufficient to crush the diamond anvil is applied. In their research, the team smashed dozens of pairs of diamond anvil worth $3,000. "This is the biggest problem in our research. The price of diamond anvil is too high." Dias said helplessly.

The successful scheme proved to be a repetition of the 20 15 scheme. The researchers added methane (a hydrocarbon) to hydrogen sulfide and then baked it with a laser.

Ashkan Salamat, Diaz's collaborator and condensed matter physicist at the University of Nevada, Las Vegas, said: "We have perfected this system. By adding the right amount of hydrogen, these Cooper pairs can still operate normally at high temperatures."

However, they failed to determine the specific details of the hydrogen-carbon-sulfur mixture they developed. Hydrogen is too small to be displayed by a probe with a traditional lattice structure, so the team doesn't know how the atoms are arranged, or even the exact chemical formula of this substance.

Eva Zurek, a computational chemist at the University of Buffalo, belongs to the theoretical group of Diaz Laboratory. Earlier this year, they hypothesized a superconducting condition that might form metal between diamond anvil, but the result was just the opposite. Zurek suspects that high pressure transforms matter into an unknown arrangement, and the matter formed by this arrangement has superconductivity.

Once Diaz's team knows what they have, theorists will be able to build a model to study the superconducting properties given to this hydrogen-carbon-sulfur mixture, and it is possible to further modify the formula that constitutes this mixture.

Physicists have proved that most binary hydrogen mixtures are not feasible, but the new ternary mixtures mark great progress in the field of complex chimera materials, and one of them may bring new hope.

"I like this job because they introduced carbon into the system." Mikhail Elmetz, an experimenter at the Max Planck Institute for Chemistry, said. His laboratory set new hydride records in 20 15 and 20 19 respectively.

He explained that using the low mass of hydrogen is not the only way to enhance vibration and let electrons form Cooper pairs. Stronger connectivity between adjacent atoms in the lattice is also important. In addition, the covalent bond of carbon has strong binding ability. Carbon structural materials have other advantages, such as how to prevent the whole structure from collapsing under comfortable low pressure conditions.

Dzurek agrees with this. She said: "I think it is difficult to achieve superconductivity under normal pressure, but if carbon compounds can be introduced into it, I think it is possible."

Source: Quanta Magazine