“Strange metals” have that name for a reason – these materials exhibit some unusual conductive properties and surprisingly, even have things in common with black holes. Now, a new study has characterized them in more detail, and found that strange metals constitute a new state of matter.
So-called strange metals differ from regular metals because their electrical resistance is directly linked to temperature. Electrons in strange metals are seen to lose their energy as fast as the laws of quantum mechanics allow. But that’s not all – their conductivity is also linked to two fundamental constants of physics: Planck’s constant, which defines how much energy a photon can carry, and Boltzmann’s constant, which relates the kinetic energy of particles in a gas with the temperature of that gas.
While these properties have been well observed over the years, scientists have had a hard time accurately modeling strange metals. So in a new study, researchers from the Flatiron Institute and Cornell University set out to solve the model, right down to absolute zero – lower than the lowest possible temperature for materials.
In doing so, the team discovered that strange metals actually represent a new state of matter. It turns out they exist between two known phases of matter – Mott insulating spin glasses and Fermi liquids – and the researchers were able to describe their properties in more detail.
“This quantum spin liquid state is not so locked down, but it’s also not completely free,” says Eun-Ah Kim, an author of the study. “It is a sluggish, soupy, slushy state. It is metallic but reluctantly metallic, and it’s pushing the degree of chaos to the limit of quantum mechanics.”
But perhaps the weirdest, most striking thing about strange metals is that they share some properties with black holes. These cosmic oddities also have properties that are tied exclusively to temperature and the Planck and Boltzmann constants, including the amount of time they “ring” after merging with other black holes.
Normally, the physics of the electrons in strange metals are far too complex for accurate calculations. There’s a huge amount of particles involved, and because electrons tend to form quantum entanglements, they can’t be treated as separate objects.
The team overcame these hurdles using two different methods. First, they used a quantum embedding method to perform complex calculations on only a few atoms, then generalize for the rest of the system. Next, they used a quantum Monte Carlo algorithm, which uses repeated random sampling to perform calculations. Together, this combination helped the team gain a better understanding of strange metals.
The team says their new model of strange metals could help physicists understand how superconductors may work at higher temperatures.
The research was published in the journal Proceedings of the National Academy of Sciences.
Source: Simons Foundation
