  The Bardeen-Cooper-Schrieffer mechanism for superconductivity is a triumph of
the theory of many-body systems. Implicit in its formulation is the existence
of long-lived (quasi)particles, originating from the electronic building blocks
of the materials, which interact to form Cooper pairs that move coherently in
lock-step. The challenge of unconventional superconductors is that it is not
only unclear what the nature of the interactions are, but whether the familiar
quasi-particles that form a superconducting condensate even exist. In this
work, we reveal, by the study of applied magnetic field in electronically
diluted materials, that the metallic properties of the unconventional
superconductor CeCoIn$_5$ are determined by the degree of quantum entanglement
that (Kondo) hybridizes local and itinerant electrons. This work suggests that
the properties of the strange metallic state are a reflection of the
disentanglement of the many-body state into the underlying electronic building
blocks of the system itself.
