Full Idea
In Field's view reference is a 'physicalistic relation', i.e. a complex causal relation between words or mental representations and objects or sets of objects; it is up to physical science to discover what that physicalistic relation is.
Gist of Idea
Field says reference is a causal physical relation between mental states and objects
Source
report of Hartry Field (Tarski's Theory of Truth [1972]) by Hilary Putnam - Reason, Truth and History Ch.2
Book Reference
Putnam,Hilary: 'Reason, Truth and History' [CUP 1998], p.45
A Reaction
I wouldn't hold your breath while the scientists do their job. If physicalism is right then Field is right, but physics seems no more appropriate for giving a theory of reference than it does for giving a theory of music.