An international team of researchers has discovered that the quantum particles responsible for the vibrations of materials—which influence their stability and various other properties—can be classified through topology.
Phonons, the collective vibrational modes of atoms within a crystal lattice, generate disturbances that propagate like waves through neighboring atoms. These phonons are vital for many properties of solid-state systems, including thermal and electrical conductivity, neutron scattering, and quantum phases like charge density waves and superconductivity.
The spectrum of phonons—essentially the energy as a function of momentum—and their wave functions, which represent their probability distribution in real space, can be computed using ab initio first principle codes. However, these calculations have so far lacked a unifying principle.
"For the quantum behavior of electrons, topology—a branch of mathematics—has successfully classified the electronic bands in materials. This classification shows that materials, which might seem different, are actually very similar. We already have catalogs of electronic topological behaviors, akin to a periodic table of compounds. Naturally, this led us to question: Can topology also characterize phonons?" explained B. Andrei Bernevig, a professor of physics at Princeton University, visiting professor at DIPC, and one of the study's authors.
In a study published in the journal Science, an international team from Princeton University, Zhejiang University, DIPC, ENS-CNRS, Max Planck Institute, and the University of the Basque Country uncovered that a wide range of materials could host topological phonons.
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