Entanglement and Bell’s inequality violation above room temperature in metal carboxylates

Abstract

In the present work we show that a particular family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic-susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the copper carboxylate ${{\text{Cu}}_{2}{({\text{O}}_{2}\text{CH})}_{4}}{\text{Cu}{({\text{O}}_{2}\text{CH})}_{2}{(2\text{-methylpyridine})}_{2}}$, and we have found this to be above room temperature $({T}_{e}\ensuremath{\sim}630\text{ }\text{K})$. Furthermore, the results show that the system remains maximally entangled until close to $\ensuremath{\sim}100\text{ }\text{K}$ and the Bell's inequality is violated up to nearly room temperature $(\ensuremath{\sim}290\text{ }\text{K})$.