Quantum Physicists Crack Mystery of “Strange Metals” – A New State of Matter

Strange metals have surprising connections to high-temperature superconductors and black holes.

Even by the standards of quantum physicists, strange metals are just plain odd. The materials are related to high-temperature superconductors and have surprising connections to the properties of black holes. Electrons in strange metals dissipate energy as fast as they’re allowed to under the laws of quantum mechanics, and the electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.

Generating a theoretical understanding of strange metals is one of the biggest challenges in condensed matter physics. Now, using cutting-edge computational techniques, researchers from the Flatiron Institute in New York City and Cornell University have solved the first robust theoretical model of strange metals. The work reveals that strange metals are a new state of matter, the researchers report July 22 in the Proceedings of the National Academy of Sciences.

“The fact that we call them strange metals should tell you how well we understand them,” says study co-author Olivier Parcollet, a senior research scientist at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ). “Strange metals share remarkable properties with black holes, opening exciting new directions for theoretical physics.”

A diagram showing different states of matter as a function of temperature, T, and interaction strength, U (normalized to the amplitude, t, of electrons hopping between sites). Strange metals emerge in a regime separating a metallic spin glass and a Fermi liquid. Credit: P. Cha et al./Proceedings of the National Academy of Sciences 2020

In addition to Parcollet, the research team consisted of Cornell doctoral student Peter Cha, CCQ associate data scientist Nils Wentzell, CCQ director Antoine Georges, and Cornell physics professor Eun-Ah Kim.

In the quantum mechanical world, electrical resistance is a byproduct of electrons bumping into things. As electrons flow through a metal, they bounce off other electrons or impurities in the metal. The more time there is between these collisions, the lower the material’s electrical resistance.

For typical metals, electrical resistance increases with temperature, following a complex equation. But in unusual cases, such as when a high-temperature superconductor is heated just above the point where it stops superconducting, the equation becomes much more straightforward. In a strange metal, electrical conductivity is linked directly to temperature and to two fundamental constants of the universe: Planck’s constant and Boltzmann’s constant. Consequently, strange metals are also known as Planckian metals.

Models of strange metals have existed for decades, but accurately solving such models proved out of reach with existing methods. Quantum entanglements between electrons mean that physicists can’t treat the electrons individually, and the sheer number of particles in a material makes the calculations even more daunting.

Cha and his colleagues employed two different methods to crack the problem. First, they used a quantum embedding method based on ideas developed by Georges in the early ’90s. With this method, instead of performing detailed computations across the whole quantum system, physicists perform detailed calculations on only a few atoms and treat the rest of the system more simply. They then used a quantum Monte Carlo algorithm (named for the Mediterranean casino), which uses random sampling to compute the answer to a problem. The researchers solved the model of strange metals down to absolute zero (minus 273.15 degrees Celsius), the unreachable lower limit for temperatures in the universe.

The resulting theoretical model reveals the existence of strange metals as a new state of matter bordering two previously known phases of matter: Mott insulating spin glasses and Fermi liquids. “We found there is a whole region in the phase space that is exhibiting a Planckian behavior that belongs to neither of the two phases that we’re transitioning between,” Kim says. “This quantum spin liquid state is not so locked down, but it’s also not completely free. 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.”

The new work could help physicists better understand the physics of higher-temperature superconductors. Perhaps surprisingly, the work has links to astrophysics. Like strange metals, black holes exhibit properties that depend only on temperature and the Planck and Boltzmann constants, such as the amount of time a black hole ‘rings’ after merging with another black hole. “The fact that you find this same scaling across all these different systems, from Planckian metals to black holes, is fascinating,” Parcollet says.

Reference: “Linear resistivity and Sachdev-Ye-Kitaev (SYK) spin liquid behavior in a quantum critical metal with spin-1/2 fermions” by Peter Cha, Nils Wentzell, Olivier Parcollet, Antoine Georges and VEun-Ah Kim, 22 July 2020, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2003179117

Materials ScienceParticle PhysicsPopularQuantum PhysicsSimons Foundation
Comments ( 19 )
Add Comment
  • Derck van Schuylenburch

    Once again:
    the right ends of yiour sentences are clipped-off because
    the alotted text space is insufficient, or your font is to large.
    Did you ever consider having your site composed by professionals, rather than high-school students?

  • Romello

    Ooooooo high school students don’t know sh*t! First shots fired! Give Derck van Schuylenburch the job, he knows what’s up! Can’t you see how diplomatic he’s being?! Like he said the ends of YIOUR sentences are clipped get it together science dorks!🤣😂🤣

    • Eric Caine

      That means the injunction of the superconductor emitting particles in front of a object will allow that object to go through the black hole that has been created by the strange material. The heat created will help create a stable black hole cool enough to pass a object through. Look over you calulations you are missing a few equation to prove your assumptions.

  • Harold Lane

    On my Android device, I chose Desktop Site on the 3-dot More Menu.That reconfigured the page to wider-but-teeny view. At the bottom of this page was a Desktop View webpage button. After clicking it, the page repaginated to break text at the margins of my phone. That should help till the designers get the kinks worked out. Fascinating topic, by-the-way…

  • Mark

    does that mean strange metals might one day make blackholes or wormholes

  • Andrew

    I guess you were to say “conductivity” rather than “resistivity”??
    “…the electrical resistivity of a strange metal, unlike that of ordinary metals, is proportional to the temperature.”

  • Shawn

    Interesting topic that I will now binge research.

    Also, thank you Harold for introducing me to the verb repaginate. 👍🏻 Your word-smithing is unparalleled sir.

  • mahakal

    jay pubg

  • Dr. Michael A Blau, D.C.

    I can see a new genre Of music coming out of this……….
    (STRANGE METAL)
    We have Heavy Metal bands.
    We have Death Metal bands
    Now we can have the craziest,most energetic/spun rock bands ever…
    STRANGE METAL BAND

  • Robert Jansen

    Lotsa folks on this site with way too much time on their hands, yes?

  • K C Christopher

    Derck Derck Derck! Dude. The phenomena you describe are caused by the device & browser YOU are using. IOW, the problem is on your end.

  • yes

    can confirm that image and image caption are cut off because they don’t fit the container. newest chrome on android. duckduckgo browser on android renders it without the cut off.
    chrome has become worse over the last updates, and slower and freezes some time. i would blame it on chrome but who am i to tell google they suck at engineering?

  • Chrischem

    Hey Derek,
    What gives you the right to criticize the writers when you don’t even know which homophone to use in your sentences. It’s “too” not “to”!

  • Fatakhsha

    Are you want to say that strange metals are going to change into black holes one day.

  • Bran Autry

    It’s astounding how ignorant of this subject people in this comment section seem to be.

  • xABBAAA

    … The world of quantum physics is just so exciting and now this.

    On the other side, students might not like that. One more lesson…

  • Barry Williams

    Derek, turn your phone sideways! SHEESH! I’m not the sharpest tool in the shed and I have no problem coping with the captions under pictures which deduce (always wanted to be Sherlock) is the problem you are referring to.

  • Barry Williams

    Damn you dastardly text box! You omitted my eye!

  • Barry Williams

    I. Damned speech to text!