Lifshits quantum phase transitions and rearrangement of the Fermi surface upon a change in the hole concentration in high-temperature superconductors
Changes in the electronic structure in the normal phase of high- T c superconductors (HTSCs), viz., layered cuprates, are considered. The results of LDA + GTB calculations of the electron structure and the Fermi surface of La 2 − x Sr x CuO 4 one-layer cuprates with allowance for strong correlations are compared with ARPES and quantum oscillations data. Two critical points x c 1 and x c 2 are discovered at which the rear-rangement of the Fermi surface takes place. In the vicinity of these points, changes in the thermodynamic properties at low temperatures are determined using the Lifshits ideology concerning 2.5-order quantum phase transitions. A singularity δ( C / T ) ∝ ( x − x e ) 1/2 in the electron heat capacity agrees well with the available experimental data in the vicinity of x c 1 ≈ 0.15. Sign reversal of the Hall constant upon doping is also considered qualitatively.