Ground state, collective mode, phase soliton and vortex in multiband superconductors.

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Multiband superconductors feature multiple energy gaps and interacting Cooper pairs.
• Discovery of MgB2 and iron-based superconductors spurred research interest.
• Recent superconductors often exhibit multiband characteristics.

Purpose of the Study:

• To review theoretical and experimental findings on novel physics in multiband superconductors.
• To highlight unique properties not found in single-band superconductors.
• To identify challenges and opportunities in multiband superconductivity research.

Main Methods:

• Survey of theoretical and experimental investigations.
• Analysis of properties such as time-reversal symmetry breaking.
• Focus on phenomena like the Leggett mode, phase solitons, and fractional vortices.

Main Results:

• Multiband superconductors exhibit unique properties, including time-reversal symmetry broken states.
• The Leggett mode, involving collective oscillations of Cooper pairs between bands, is a key feature.
• Phase solitons and fractional vortices represent significant areas of novel physics.

Conclusions:

• Multiband superconductors possess unusual and unique properties.
• Further research is needed to address challenges and explore opportunities in this field.
• Understanding these systems offers insights into fundamental superconductivity mechanisms.