Bose Metals, from Prediction to Realization.

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• Bose metals represent an intermediate phase between superconductivity and superinsulation.
• Their existence was theoretically predicted in the mid-1990s based on topological quantum effects.
• Understanding Bose metals is crucial for advancing quantum phenomena research.

Purpose of the Study:

• To review the fundamental mechanism driving the formation of Bose metals.
• To validate the theoretical prediction of Bose metals in Josephson junction arrays.
• To elucidate the role of topological quantum effects in this metallic phase.

Main Methods:

• Analysis of Cooper pair behavior in superconducting films and Josephson junction arrays.
• Investigation of core-less, mobile XY vortices and quantum phase slips.
• Examination of topological mutual statistics interactions between charges and vortices.

Main Results:

• Experimental observation of Bose metals in regular Josephson junction arrays confirms theoretical predictions.
• The study rules out disorder-based models, highlighting topological quantum effects.
• Repulsive topological interactions lift Cooper pairs out of the condensate, forming a topological ground state.

Conclusions:

• The observed metallic saturation at low temperatures is explained by edge charge conduction and vortex movement.
• Bose metals are a direct consequence of quantum phase slips and topological interactions.
• This metallic phase is identified as a bosonic topological insulator, validating prior theoretical work.