IBM Scientists Observe Elusive Gravitational Effect in Solid-State Physics

July 19, 2017

An international team of physicists, material scientists and string theoreticians have observed a phenomenon on Earth which was previously thought to only occur hundreds of light years away or at the time when the universe was born. This result could lead to a more evidence-based model for the understanding the universe and for improving the energy-conversion process in electronic devices.
Using a recently discovered material called a Weyl semimetal, similar to 3D graphene, scientists from IBM Research mimicked a gravitational field in their test sample by imposing a temperature gradient. The study was supervised by Prof. Kornelius Nielsch, Director of the Leibniz Institute for Solid State and Materials Research as well as by Prof. Claudia Felser, Director at the Max-Planck-Institute for Chemical Physics of Solids in Dresden.

After conducting the experiment at a cryolab at the University of Hamburg in high magnetic fields, a team of theoreticians from TU Dresden, UC Berkeley and the University of Madrid confirmed with detailed calculations that they observed a quantum anomaly known as axial-gravitational anomaly which breaks one of the classical conservation laws, such as charge, energy and momentum.
This law-breaking anomaly had been previously derived on purely theoretical reasoning with methods based on string theory. It was believed to only exist at high temperatures, in the trillions of degrees, as an exotic form of matter, called a quark-gluon plasma, from the early stages of the universe deep within the cosmos or created using particle colliders. But to the surprise of the authors they discovered it also exists on Earth in the properties of solid state physics, which much of the computing industry is based on, spanning from tiny transistors to cloud data centers. The discovery is appearing today in the peer-review journal Nature.

“For the first time, we have experimentally observed this fundamental quantum anomaly on Earth which is extremely important towards our understanding of the universe,” said Dr. Johannes Gooth, an IBM Research scientist and lead author of the paper. “We can now build novel solid state devices based on this anomaly which have never been considered before to potentially circumvent some of the problems inherent to classical electronic devices, such as transistors.”

“This is an incredibly exciting discovery. We can clearly conclude that the same breaking of symmetry can be observed in any physical system, whether it’s from the beginning of the universe or today, right here on Earth,” said Prof. Dr. Karl Landsteiner, a string theorist at the Instituto de Fisica Teorica UAM/CSIC and co-author of the paper.

IBM scientists predict this discovery will open up a rush of new developments around sensors, switches and thermoelectric coolers or energy harvesting devices, for improved power consumption.

Read more at: Join the conversation on Twitter @IBMResearch and #axialanomaly

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This work was supported by the research grant DFG-RSF (NI616 22/1): Contribution of topological states to the thermoelectric properties of Weyl semimetals and SFB 1143 as well as by the Helmholtz association through VI-521 and the DFG (Emmy-Noether programme) via grant ME 4844/1. Additional grants include: SEV-2012-0249 and FPA2015-65480-P.

Experimental signatures of the mixed axial-gravitational anomaly in the Weyl semimetal NbP, Johannes Gooth, Anna C. Niemann, Tobias Meng, Adolfo G. Grushin, Karl Landsteiner, Bernd Gotsmann, Fabian Menges, Marcus Schmidt, Chandra Shekhar, Vicky Süß, Ruben Hühne, Bernd Rellinghaus, Claudia Felser, Binghai Yan, Kornelius Nielsch, DOI: 10.1038/nature23005


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