Balz, C.; Lake, B.; Luetkens, H.; Baines, C.; Guidi, T.; Abdel-Hafiez, M.; Wolter, A.U.B.; Buechner, B.; Morozov, I.V.; Deeva, E.B.; Volkova, O.S.; Vasiliev, A.N.: Publisher's Note: Quantum spin chain as a potential realization of the Nersesyan-Tsvelik model. Physical Review B 90 (2014), p. 099901/1-1

It is well established that long-range magnetic order is suppressed in magnetic systems whose interactions are low dimensional. The prototypical example is the S- 1 2 Heisenberg antiferromagnetic chain (S- 1/2 HAFC) whose ground state is quantum critical. In real S- 1/2 HAFC compounds interchain coupling induces long-range magnetic order although with a suppressed ordered moment and reduced N´eel temperature compared to the Curie-Weiss temperature. Recently, it was suggested that order can also be suppressed if the interchain interactions are frustrated, as for the Nersesyan-Tsvelik model. Here, we study the new S- 1/2 HAFC, (NO)[Cu(NO3)3]. This material shows extreme suppression of order which furthermore is incommensurate revealing the presence of frustration consistent with the Nersesyan-Tsvelik model.