On the two types of vortexlike excitations in the pseudogap state of an underdoped high-Tc superconductor

Abstract

A model of charge transport for U stripes of the pseudogap state of underdoped cuprate high-Tc superconductors is discussed which is topologically consistent with antiferromagnetism. The stripe structure of the CuO2 plane at T<T*(p) suggests that on doping the Cu2+ ions localize the holes, forming planar nonmagnetic Cu3+O42− “molecules” with a nondegenerate A state of the Cu3+ ion. It is shown that in U stripes the vibronic A→E transitions of the Cu3+ ions to the degenerate E state of the Cu2+ ion occur with the release of an energy ΔU, which for T2D≤T≤T*(p) gives rise to a two-dimensional gas of vortices and antivortices “pinned” by complexes Cu↑2+O42−(or Cu↓2+O42−). When the temperature is lowered, T<Tf(p), a transition of the U stripes occurs to a two-dimensional (2D) vortex-metal state with non-Fermi charge carriers (mobile 2D vortices and antivortices) which are consistent with antiferromagnetic order of the CuO2 plane. With the development of 2D superconducting fluctuations at T2D≤T≤T*(p) the pairing of vortices and antivortices renormalizes the interplane interaction constant, and the dimensional crossover 2D→3D occurs before the Berezinskii–Kosterlitz–Thouless transition. Upon further lowering of the temperature, the superconducting transition occurs by the Kats scenario at Tc>TBKT with a bounded interval of 3D superconducting fluctuations. It is shown that a two-component model of charge carriers which are topologically consistent with antiferromagnetism of the doped CuO2 plane is in agreement with the observation of electric signals at T2D≤T≤T*(p) [Y. Wang et al., Phys. Rev. B 64, 224519 (2001)].