Thermal entanglement in the nanotubular system Na_2V_3O_7

Abstract

Macroscopic entanglement witnesses have been put forward recently to reveal nonlocal quantum correlations between individual constituents of the solid at nonzero temperatures. Here we apply a recently proposed universal entanglement witness, the magnetic susceptibility [New J. Phys. {\bf 7}, 258 (2005)] for the estimation of the critical temperature $T_c$ in the nanotubular system $\mathrm{N}{\mathrm{a}}_2{\mathrm{V}}_3{\mathrm{O}}_7$ below which thermal entanglement is present. As a result of an analysis based on the experimental data for dc-magnetic susceptibility, we show that $T_c\approx 365$ K, which is approximately three times higher than the critical temperature corresponding to the bipartite entanglement.

6 pages, 3 figures, REVTeX4