In many Fermi systems and compounds at zero temperature a phase transition occurs that leads to a specific state called fermion condensation. As a signal of the fermion condensation quantum phase transition serves unlimited increase of the effective mass of quasiparticles that determines the excitation spectrum and creates flat bands [1]. We have theoretically carried out a systematic study of the phase diagrams of strongly correlated Fermi systems, including heavy-fermion metals, high temperature superconductors, insulators with strongly correlated quantum spin liquid, quasicrystals, two dimensional Fermi systems (like ³He), one-dimensional spin liquids, and have demonstrated that these diagrams have universal features.

The obtained results are in good agreement with experimental facts. We have shown both analytically and using arguments based entirely on the experimental grounds that the data collected on these very different heavy-fermion compounds have a universal scaling behavior, and these materials with strongly correlated fermions can unexpectedly have a uniform behavior in spite of their microscopic diversity [1, 2].

Thus, the quantum critical physics of different Fermi systems is universal, defined by topological fermion condensation quantum phase transition, and emerges regardless of the underlying microscopic details of compounds.

References

1. V. R. Shaginyan, M. Ya. Amusia, A. Z. Msezane, and K. G. Popov, “Scaling Behavior of Heavy Fermion Metals”, Phys. Rep. 492, 31 (2010). 

2. M. Ya. Amusia, K. G. Popov, V. R. Shaginyan, and V. A. Stephanowich, Theory of Heavy-Fermion Compounds - Theory of Strongly Correlated Fermi-Systems, Springer Series in Solid-State Sciences 182, (2015).