Superconductivity.

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Electrons in metals exhibit self-organization, leading to diverse electronic orders.
• Superconductivity, a phenomenon of perfect conductivity and diamagnetism, has been studied for nearly a century.
• The interplay of lattice dynamics, electrostatic interactions, and band structure governs electronic order.

Purpose of the Study:

• To introduce fundamental experimental signatures of superconductivity: perfect conductivity and perfect diamagnetism.
• To explain these signatures using a broken symmetry argument and the Bardeen-Cooper-Schrieffer (BCS) model.
• To discuss novel forms of superconductivity in new materials that deviate from the conventional BCS theory.

Main Methods:

• Review of fundamental experimental signatures of superconductivity.
• Explanation through a broken symmetry argument and introduction of a superconducting order parameter.
• Discussion of the microscopic origin within the BCS model.
• Exploration of novel superconducting materials and their properties.

Main Results:

• Fundamental signatures of superconductivity (perfect conductivity, perfect diamagnetism) are explained.
• The BCS model provides a microscopic framework for conventional superconductivity.
• Numerous novel superconducting materials exist, including high-temperature, organic, and d-/f-metal compounds, which fall outside the orthodox BCS model.

Conclusions:

• Superconductivity is a complex phenomenon driven by electron self-organization with distinct experimental signatures.
• The BCS model successfully explains conventional superconductivity, but new materials necessitate expanded theoretical frameworks.
• Further research is needed to understand the puzzling behavior of novel superconductors above their transition temperatures.