Thermal fluctuations near a phase transition probed through the electrical resistivity of high-temperature superconductors

Abstract

We present a simple and inexpensive experimental setup that can determine the thermal fluctuations near a superconducting transition. By using equipment common in undergraduate laboratories, the in-plane dc electrical resistivity of a cuprate superconductor as a function of temperature is measured with resolution sufficient to analyze the fluctuation conductivity above the superconducting critical temperature, including the values of the critical exponents. We also present a simple calculation of the fluctuation conductivity, including its dependence on the layered structure of the material, within the Gaussian–Ginzburg–Landau formalism.

High harmonic spectroscopy of quantum phase transitions in a high-Tc superconductor

“…The HHS measurement clearly shows a departure from the normal conducting phase with an increased formation of Cooper pairs upon cooling. The variation in harmonic orders is linked to phenomenological energy and phase relaxation times, which identify the transition to the fluctuation regime (35,36), i.e., between the strange metal and pseudogap phases, and the sudden transition at T c into the superconducting phase. Unconventional superconductors, like YBCO, are material systems in which the formation of composite bosons out of paired fermions is mediated not by phonon exchange but by some other kind of energy exchange (37), for instance, due to spin fluctuations.…”

High harmonic spectroscopy of quantum phase transitions in a high-T$_c$ superconductor

“…The HHS measurement clearly shows a departure from the normal conducting phase with an increased formation of Cooper pairs upon cooling. The variation in harmonic orders is linked to phenomenological energy and phase relaxation times, which identify the transition to the fluctuation regime [24,25], i.e. between the strange metal and pseudogap phases, and the sudden transition at T c into the superconducting phase.…”