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Rice University researchers have discovered a novel three-dimensional crystalline metal that locks electrons in place due to a unique interplay of quantum correlations and the geometric structure of the material. This discovery highlights the role of planar electronic bands in determining the properties of a material and lays the foundation for future explorations of quantum materials with pyrochlore lattice structures. Credit: SciTechDaily.com
New research validates the method for guided discovery of 3D flat web materials.
Rice University scientists have discovered a first-of-its-kind material: a three-dimensional crystalline metal in which quantum correlations and the geometry of the crystal structure combine to thwart the movement of electrons and lock them in place.
The finding is detailed in a study published in Nature physics. The article also describes the theoretical design principle and experimental methodology that guided the research team to the material. One part copper, two parts vanadium and four parts sulfur, the alloy presents a 3D pyrochlore network consisting of tetrahedra that share corners.
Quantum entanglement and electron localization
“We are looking for materials in which there are potentially new states of matter or new exotic features that have not been discovered,” said study co-author Ming Yi, an experimental physicist at Rice.
Quantum materials are a likely place to look, especially if they host strong electronic interactions that give rise to quantum entanglement. Entanglement leads to strange electronic behaviors, including frustrating the movement of electrons to the point where they become locked in place.
“This quantum interference effect is analogous to waves propagating across the surface of a pond and meeting head-on,” Yi said. “The collision creates a standing wave that does not move. “In the case of geometrically frustrated lattice materials, it is the electronic wave functions that destructively interfere.”
Jianwei Huang, a postdoctoral research associate at Rice University, with the laboratory apparatus he used to perform angle-resolved photoemission spectroscopy experiments on a copper-vanadium alloy. The experiments showed that the alloy is the first known material in which the three-dimensional crystal structure and strong quantum interactions frustrate the movement of electrons and lock them in place, resulting in a flat electronic band. Credit: Jeff Fitlow/Rice University
The localization of electrons in metals and semimetals produces flat electronic bands or flat bands. In recent years, physicists have discovered that the geometric arrangement of atoms in some two-dimensional crystals, such as Kagome lattices, can also produce flat bands. The new study provides empirical evidence of the effect in a 3D material.
Advanced techniques and surprising findings
Using an experimental technique called angle-resolved photoemission spectroscopy, or ARPES, Yi and the study’s lead author, Jianwei Huang, a postdoctoral researcher in her lab, detailed the band structure of the copper-vanadium-sulfur material and found that it harbored a flat band that is unique in several ways.
“It turns out that both types of physics are important in this material,” Yi said. “The geometric aspect of frustration was there, as theory had predicted. The pleasant surprise was that there were also correlation effects that produced the flat band at the Fermi level, where it can actively participate in determining physical properties.”
Jian Wei Huang. Credit: Jeff Fitlow/Rice University
In solid matter, electrons occupy quantum states that are divided into bands. These electronic bands can be thought of as rungs on a ladder, and electrostatic repulsion limits the number of electrons that can occupy each rung. The Fermi level, an inherent property of materials and crucial in determining their band structure, refers to the energy level of the highest occupied position on the ladder.
Theoretical ideas and future directions
Rice theoretical physicist and study co-author Qimiao Si, whose research group identified the copper-vanadium alloy and its pyrochlore crystal structure as a possible host for the combined frustrating effects of geometry and strong electron interactions, He compared the discovery to the discovery of a new continent. .
“It’s the first work to really show not only this cooperation between geometry-driven frustration and interaction, but also the next stage, which is getting the electrons to be in the same space at the top of the (energy) ladder. ), where there is a maximum possibility of them being reorganized into interesting and potentially functional new phases,” Si said.
He said the predictive methodology or design principle his research group used in the study may also be useful to theorists studying quantum materials with other crystal lattice structures.
“Pyrochloro is not the only game out there,” Si said. “This is a new design principle that allows theorists to predictively identify materials in which flat bands arise due to strong electronic correlations.”
Yi said there is also plenty of room for further experimental exploration of pyrochlore crystals.
“This is just the tip of the iceberg,” he said. “This is 3D, which is new, and considering how many surprising finds there have been in Kagome networks, I imagine there could be equally or even more exciting discoveries in pyrochlore materials.”
Reference: “Behavior of non-Fermi liquids in a correlated flat-band pyrochlore lattice” by Jianwei Huang, Lei Chen, Yuefei Huang, Chandan Setty, Bin Gao, Yue Shi, Zhaoyu Liu, Yichen Zhang, Turgut Yilmaz, Elio Vescovo, Makoto Hashimoto, Donghui Lu, Boris I. Yakobson, Pengcheng Dai, Jiun-Haw Chu, Qimiao Si and Ming Yi, January 26, 2024. Nature physics.
DOI: 10.1038/s41567-023-02362-3
The research team included 10 Rice researchers from four laboratories. Physicist Pengcheng Dai’s research group produced the numerous samples needed for experimental verification, and Boris Yakobson’s research group in the Department of Materials Science and NanoEngineering performed first-principle calculations that quantified the flat band effects produced by the geometric frustration. The ARPES experiments were carried out at Rice and at the SLAC National Accelerator Laboratory’s Stanford Synchrotron Radiation Light Source in California and the Brookhaven National Laboratory’s National Synchrotron Light Source II in New York, and the team included collaborators from SLAC, Brookhaven and the University of Washington.
The research used resources supported by a Department of Energy (DOE) contract for SLAC (DE-AC02-76SF00515) and was supported by grants from the Gordon and Betty Moore Foundation’s Emerging Phenomena in Quantum Systems Initiative (GBMF9470), the Robert A. Welch Foundation. Foundation (C-2175, C-1411, C-1839), the DOE Office of Basic Energy Sciences (DE-SC0018197), the Air Force Office of Scientific Research (FA9550-21-1-0343, FA9550-21 -1- 0356), the National Science Foundation (2100741), the Office of Naval Research (ONR) (N00014-22-1-2753), and the Vannevar Bush Faculty Fellows program administered by the ONR’s Office of Basic Research Department of Defense (ONR-VB N00014-23-1-2870).