Novel physical phenomena in proximity to quantum critical point

Abstract

AbstractThe weakly interacting quasiparticle picture of a Fermi liquid proposed by Landau (the phonon‐mediated electron‐pairing theory of Bardeen–Cooper–Schrieffer) provided a coherent theoretical basis for understanding how the interactions between electrons affect the low‐temperature properties of metals (metallic superconductors) for the past five decades. However, in recent years, strong departures from the predictions of these theories have been observed in an increasingly large number of systems, particularly in the vicinity of a quantum phase transition (QPT). This paper briefly reviews the current state of research in the areas of the non‐Fermi liquid (NFL) state, spin‐fluctuation‐mediated anisotropic superconductivity, and Bose–Einstein condensation (BEC) of magnons (bosonic quasiparticle excitations) near a quantum critical point (QCP), which is induced by external pressure or doping or nanocrystallite size or magnetic fields.