Nanowerk May 26, 2021
Usually, quantum critical behaviour is studied in metals or insulators. But an international team of researchers (USA – Johns Hopkins University, University of Maryland, NIST, Rice University, Austria) looked at a semimetal which is a compound of cerium, ruthenium, and tin – with properties that lie between those of metals and semiconductors. Usually, quantum criticality can only be created under specific environmental conditions however, this semimetal turned out to be quantum critical without any external influences at all. They suspect that it may be because it has a highly correlated electron system where the electrons interact strongly with each other leading to the Kondo effect. A quantum spin in the material is shielded by electrons surrounding it, so that the spin no longer has any effect on the rest of the material. The system fluctuates between a state with and a state without the Kondo effect, and this has the effect of a phase transition at zero temperature. It seems to them that quantum critical fluctuations, the Kondo effect and Weyl fermions – are tightly intertwined in the material and, together, give rise to exotic Weyl-Kondo states. Further measurements under different external conditions are required to verify this. The team expects that a similar interplay of the various quantum effects should also be found in other materials…read more. Open Access TECHNICAL ARTICLEÂ
Signatures of quantum criticality in thermodynamic properties of CeRu4Sn6. Credit: Science Advances 19 May 2021, Vol. 7, no. 21, eabf9134Â