Lifshits quantum phase transitions and rearrangement of the Fermi surface upon a change in the hole concentration in hig
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SORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Lifshits Quantum Phase Transitions and Rearrangement of the Fermi Surface upon a Change in the Hole Concentration in HighTemperature Superconductors S. G. Ovchinnikova,b,e*, M. M. Korshunova,c,d, and E. I. Shneydera,e a
Kirenskii Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia b Siberian Federal University, Krasnoyarsk, 660041 Russia c MaxPlanckInstitut für Physik Komplexer Systeme, D01187 Dresden, Germany d Department of Physics, University of Florida, Gainesville, Florida, 32611 USA e Reshetnikov Siberian State Aerospace University, Krasnoyarsk, 660014 Russia *email: [email protected] Received April 17, 2009
Abstract—Changes in the electronic structure in the normal phase of highTc superconductors (HTSCs), viz., layered cuprates, are considered. The results of LDA + GTB calculations of the electron structure and the Fermi surface of La2 – xSrxCuO4 onelayer cuprates with allowance for strong correlations are compared with ARPES and quantum oscillations data. Two critical points xc1 and xc2 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 2.5order quantum phase transitions. A singularity δ(C/T) ∝ (x – xe)1/2 in the electron heat capacity agrees well with the available experimental data in the vicinity of xc1 ≈ 0.15. Sign reversal of the Hall constant upon doping is also consid ered qualitatively. PACS numbers: 64.70.Tg, 71.10.w, 74.25.Jb DOI: 10.1134/S1063776109110077
1. INTRODUCTION HTSC cuprates have been actively studied for more than 20 years and are apparently the best studied class of condensed systems (save for the semiconductor family). The properties of cuprates were found to be peculiar. Not only the origin and mechanisms of superconductivity, but also anomalous properties of the “normal” phase (and primarily the pseudogap state; see reviews [1–8]) are unusual. Vast information on the electronic structure of cuprates was obtained using angleresolved photoelectron spectroscopy (ARPES) [9], which revealed the rearrangement of the Fermi surface from Fermi arcs at the center of the Bril louin zone at low doping levels into large hole pockets centered at point (π, π) at high doping levels. New results of measurements of quantum oscillations in strong magnetic fields obtained during the last two years for YBa2Cu3O6.5 [10] and YBa2Cu4O8 [11, 12] single crystals, and which indicate the existence of small hole pockets for weakly doped compounds, apparently contradict the Fermi arcs detected by ARPES. This contradiction was removed by taking into account the interaction of holes with shortorder antiferromagnetic (AFM) fluctuations, which are strong in the pseudogap state [13–16]. It was found that half a hole pocket is formed by shadowband
states and is blurred due to strong scattering of quasi particles from these fluctuations. Th
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