Phase fluctuations and the pseudogap in YBa(2)Cu(3)O (x)

Area of Science:

• Condensed Matter Physics
• Materials Science
• Thermodynamics

Background:

• Superconductivity in cuprates like YBa2Cu3Ox is a complex phenomenon influenced by doping.
• Understanding the superconducting transition and its relationship to the pseudogap is crucial for materials science.
• Mean-field theory provides a baseline for superconducting critical temperatures (T(MF)(c)).

Purpose of the Study:

• To investigate the thermodynamics of the superconducting transition in YBa2Cu3Ox single crystals as a function of doping.
• To elucidate the role of phase fluctuations in suppressing the critical temperature (Tc) in underdoped YBa2Cu3Ox.
• To explore the connection between the pseudogap energy and the mean-field critical temperature (T(MF)(c)).

Main Methods:

• High-resolution expansivity measurements on YBa2Cu3Ox single crystals.
• Monte Carlo simulations utilizing the anisotropic 3D- XY model.
• Analysis of thermodynamic data to determine the superconducting transition and fluctuation effects.

Main Results:

• Direct evidence showing that phase fluctuations significantly suppress Tc from T(MF)(c) in underdoped YBa2Cu3Ox.
• Demonstration that fluctuation effects are minimal in overdoped YBa2Cu3Ox, where Tc approximates T(MF)(c).
• Observation that T(MF)(c) follows a similar doping dependence as the pseudogap energy.

Conclusions:

• Phase fluctuations critically impact the superconducting transition in underdoped YBa2Cu3Ox.
• The pseudogap likely originates from phase-incoherent Cooper pairing, as suggested by the correlation between pseudogap energy and T(MF)(c).
• These findings offer insights into the mechanisms governing superconductivity in high-temperature superconductors.