When a band falls flat: Searching for flatness in materials

Date:
March 30, 2022
Source:
Max Planck Institute for Chemical Physics of Solids
Summary:
The world's first catalog of flat band materials could reduce
the serendipity in the search for new materials with exotic
quantum properties, such as magnetism and superconductivity, with
applications in memory devices or in long-range dissipationless
transport of power.



FULL STORY ========================================================================== Finding the right ingredients to create materials with exotic quantum properties has been a chimera for experimental scientists, due to the
endless possible combinations of different elements to be synthesized.


==========================================================================
From now on, the creation of such materials could be less blindfolded
thanks to an international collaboration led by Andrei Bernevig,
Ikerbasque visiting professor at Donostia International Physics Center
(DIPC) and professor at Princeton University, and Nicolas Regnault,
from Princeton University and the Ecole Normale Supe'rieure Paris, CNRS, including the participation of Luis Elcoro from the University of the
Basque Country (UPV/EHU).

The team conducted a systematic search for potential candidates in a
massive haystack of 55,000 materials. The elimination process started
with the identification of the so-called flat band materials, that is, electronic states with constant kinetic energy. Therefore, in a flat band
the behavior of the electrons is governed mostly by the interactions
with other electrons. However, researchers realized that flatness is
not the only requirement, because when electrons are too tightly bound
to the atoms, even in a flat band, they are not able to move around
and create interesting states of matter. "You want electrons to see
each other, something you can achieve by making sure they are extended
in space. That's exactly what topological bands bring to the table,"
says Nicolas Regnault.

Topology plays a crucial role in modern condensed matter physics as
suggested by the three Nobel prizes in 1985, 1997 and 2016. It enforces
some quantum wave functions to be extended making them insensitive to
local perturbation such as impurities. It might impose some physical properties, such as a resistance, to be quantized or lead to perfectly conducting surface states.

Fortunately, the team has been at the forefront of characterizing
topological properties of bands through their approach known as
"topological quantum chemistry," thereby giving them a large database
of materials, as well as the theoretical tools to look for topological
flat bands.

By employing tools ranging from analytical methods to brute-force
searches, the team found all the flat band materials currently known
in nature. This catalogue of flat band materials is available online
https:// www.topologicalquantumchemistry.fr/flatbands with its own
search engine. "The community can now look for flat topological bands in materials. We have found, out of 55,000 materials, about 700 exhibiting
what could potentially be interesting flat bands," says Yuanfeng Xu,
from Princeton University and the Max Planck Institute of Microstructure Physics, one of the two lead authors of the study. "We made sure that the materials we promote are promising candidates for chemical synthesis," emphasizes Leslie Schoop from the Princeton chemistry department. The
team has further classified the topological properties of these bands, uncovering what type of delocalized electrons they host.

Now that this large catalogue is completed, the team will start growing
the predicted materials to experimentally discover the potential myriad
of new interacting states. "Now that we know where to look, we need to
grow these materials," says Claudia Felser from the Max Planck Institute
for Chemical Physics of Solids. "We have a dream team of experimentalists working with us.

They are eager to measure the physical properties of these candidates
and see which exciting quantum phenomena will emerge." The catalogue of
flat bands, published in Natureon 30 March 2022, represents the end of
years of research by the team. "Many people, and many grant institutions
and universities to which we presented the project said this was too
hard and could never be done. It took us some years, but we did it,"
said Andrei Bernevig.

The publication of this catalogue will not only reduce the serendipity
in the search for new materials, but it will allow for large searches of compounds with exotic properties, such as magnetism and superconductivity,
with applications in memory devices or in long-range dissipationless
transport of power.

Funding Funding for the project was primarily provided by an advanced
grant of the European Research Council (ERC) at DIPC (SUPERFLAT,
ERC-2020-ADG).


========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Chemical_Physics_of_Solids.

Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* An_artistic_representation_of_band_dispersions ========================================================================== Journal Reference:
1. Nicolas Regnault, Yuanfeng Xu, Ming-Rui Li, Da-Shuai Ma, Milena
Jovanovic, Ali Yazdani, Stuart S. P. Parkin, Claudia Felser,
Leslie M.

Schoop, N. Phuan Ong, Robert J. Cava, Luis Elcoro,
Zhi-Da Song, B. Andrei Bernevig. Catalogue of flat-band
stoichiometric materials. Nature, 2022; 603 (7903): 824 DOI:
10.1038/s41586-022-04519-1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220330141422.htm

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