Amazing stuff, however under extreme conditions! How esoteric is this research?
"At TU Wien, researchers have discovered a state in a quantum material that had previously been considered impossible. The definition of topological states should be generalized. ...
Even more modern approaches are based on this particle picture—such as the concept of topological states, whose discovery was honored with the Nobel Prize in Physics in 2016. However, there are materials in which the particle picture completely breaks down ... In such cases, it no longer makes sense to think of electrons as small particles with a well-defined position or a unique velocity.
Now, a research team at TU Wien has shown that such materials can nevertheless exhibit topological properties—even though these have so far been explained using particle-like behavior. This demonstrates that topological states are more general than previously thought: two seemingly contradictory concepts turn out to be compatible. ...
the charge carriers [electrons] lose their particle-like character. This seems to happen in the material composed of cerium, ruthenium and tin (CeRu₄Sn₆), which has now been investigated at TU Wien at extremely low temperatures. “Near absolute zero, it exhibits a specific type of quantum-critical behavior,” ... “The material fluctuates between two different states, as if it cannot decide which one it wants to adopt. In this fluctuating regime, the quasiparticle picture is thought to lose its meaning.” ..."
From the abstract:
"The electronic topology of a material is generally described by its Bloch states and the associated band structure, and can be altered by electron–electron interactions.
In metallic systems, the interactions are usually treated through the concept of quasiparticles. Here we investigate what happens if no well-defined quasiparticles are present and show that a topological semimetal phase can emerge from the material’s quantum critical state.
Using the non-centrosymmetric heavy-fermion compound CeRu4Sn6, which is intrinsically quantum critical, we show that the topological phase exhibits a dome structure as a function of the magnetic field and pressure.
To understand these results, we study a Weyl–Kondo semimetal model at a Kondo destruction quantum critical point. Indeed, it exhibits features in the spectral function that can define topological crossings beyond the quasiparticle picture. Our results outline the importance of the interplay of quantum critical fluctuations and symmetry to search for other emergent topological phases."
Quantum Physics: New State of Matter Discovered (original news release) "At TU Wien, researchers have discovered a state in a quantum material that had previously been considered impossible. The definition of topological states should be generalized."
Emergent topological semimetal from quantum criticality (open access)
Fig. 5: Kondo destruction quantum criticality nucleating a Weyl–Kondo semimetal.
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