Bose metal

March 7, 2025

A research team from China and Japan has discovered compelling evidence that niobium diselenide (NbSe₂) demonstrates characteristics of a Bose metal, a quantum state that has long been theorized but remains unproven.
Definition: A Bose metal is a quantum metallic state where Cooper pairs exist but do not condense into a superconducting phase. It exhibits conductivity between that of a superconductor (infinite conductivity) and an insulator (zero conductivity) at temperatures near absolute zero.
Key Features:

Formation of Cooper Pairs:Electrons experience an attractive force, forming Cooper pairs (similar to superconductors).
Absence of Superconducting Coherence:Despite pairing, these particles fail to establish long-range superconducting order.
Intermediate Conductivity:Conductivity remains finite—neither infinite (as in superconductors) nor zero (as in insulators).
Magnetic Field Sensitivity:Strong magnetic fields can disrupt or modify the behavior of a Bose metal.

No Practical Applications Yet:Currently, Bose metals have no widespread industrial use, but they hold potential for future quantum electronic applications.
Experimental Challenges:Requires precise control of temperature, material thickness, and magnetic fields for study.
Ambiguous Definition:Ongoing debate whether Bose metals are a distinct quantum state or just a transition phase between superconductors and insulators.