Many different physicists interested in quantum mechanics to particle physics are interested in strange metals. One explanation is that, at least when exposed to extremely low temperatures, they have an abnormally high conductivity, which may make them superconductors for quantum computing.

Physicists at the University of Cincinnati are learning about the bizarre behavior of “foreign metals,” which operate outside the normal rules of electricity. In an international experiment, physicists used a strange metal made from an alloy of ytterbium. They then fired radioactive gamma rays at the peculiar metal to observe its unusual electrical behavior.

Hisao Kobayashi of the University of Hyogo and RIKEN said: “The idea is that in metal you have a sea of ​​electrons moving in the background on a lattice of ions. But something amazing is happening with quantum mechanics. You can forget about the complications of the ion lattice. Instead, they behave as if they are in a vacuum.”

For years, theoretical physicist Yashar Komijani, an assistant professor in UC’s College of Arts and Sciences, has explored the mysteries of strange metals in relation to quantum mechanics.

He said, “You can put something in a black box and I can tell you a lot about what’s inside without even looking at it by measuring things like resistivity, heat capacity and conductivity.”

“But when it comes to foreign metals, I have no idea why they behave the way they do. Why does the charge fluctuate so slowly in a highly correlated quantum system?”

Study co-author Piers Coleman, a distinguished professor at Rutgers University, said: “The exciting thing about these new results is that they provide new insight into the inner machinery of the strange metal.”

“These metals provide the canvas for new forms of electronic matter — especially exotic high-temperature superconductivity.”

“It’s too early to speculate on what new technologies might inspire strange metals.”

“It is said that after Michael Faraday discovered electromagnetism, British Chancellor William Gladstone asked what it would be good for. Faraday replied that while he didn’t know, he was sure the government would one day tax it.

“We kind of feel the same way about the strange metal,” Coleman said. “Metals play such a central role today – copper, the archetypal conventional metal, is in all appliances, all power lines, all around us.”

“Foreign metals could one day be just as ubiquitous in our technology.”

“The big question about strange metals – is the origin of their scale invariance – their ‘quantum critique.’ While the experimenters will try to replicate our results on other strange metals, our team at UC and Rutgers will try to wrap our discovery into a new theory of the foreign metals.”

Komijani said, “In Japan they use a synchrotron like they have at CERN [the European Organization for Nuclear Research] that accelerates a proton and slams it into a wall, and it emits gamma rays. So they have an on-demand source of gamma rays without using radioactive material.”

Using spectroscopy, scientists studied the effects of gamma rays on the strange metal. They also examined the speed of the metal’s electrical charge fluctuations, which last only a nanosecond – one billionth of a second.

Komijani said, “However, in the quantum world, a nanosecond is an eternity. For a long time we have wondered why these fluctuations are so slow. We came up with a theory with employees that there could be vibrations from the grille, and indeed there was.

Magazine reference:

  1. Hisao Kobayashi et al. Observation of a critical mode of charge in a foreign metal. Science. DOI: 10.1126/science.abc4787