engleski

Charge Order in Cuprates: Formation, Dynamics and Interaction With Superconductivity

In this thesis, an experimental investigation of charge stripe order in cuprate superconductors is presented. Several lanthanum-based cuprate compounds are taken as model systems for studying charge order physics. Multiple experimental techniques are employed: nuclear magnetic resonance as a local probe, linear and nonlinear conductivity for investigating transport properties and broken symmetries, and specific heat as a thermodynamic probe. The use of complementary experiments provides an overarching picture of the influence of disorder on charge stripe formation, their dynamical properties, and relation with superconductivity. It is found that the charge stripes form through an unconventional precursor charge nematic phase, which only breaks orientational symmetry and is insensitive to disorder, in agreement with previous theoretical work by other groups. We find that the stripes themselves do not appear as a well-defined phase, but always remain short-range ordered. Furthermore, the charge stripes are strongly pinned to lattice defects and are virtually static, but induce strong spin fluctuations which are dynamically decoupled from the charge stripes and display glassy freezing. The stripes strongly influence superconductivity, inducing a decoupling of copper-oxygen planes in cuprates and ushering in a quasi-two-dimensional superconducting state with ultraslow characteristic dynamics. Yet this state is unique to the charge- ordered compounds, showing that cuprate superconductivity in general is not essentially two- dimensional.

cuprates, high-temperature superconductivity, charge order, electronic liquid crystal, nuclear magnetic resonance, nonlinear conductivity

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