Electron-lattice coupling and broken symmetries of the molecular salt (TMTTF)2SbF6 -: art. no. 121101

The temperature/pressure phase diagram for (TMTTF)(2)SbF6 is determined using C-13 NMR spectroscopy. At ambient pressure, a transition to a charge-ordered (CO) state occurs at T-CO=156 K, and antiferromagnetic (AF) order is observed below T-N=8 K. Both are suppressed with pressure: when P>0.5 GPa, there is no evidence for CO, and the low-temperature C-13 NMR spectrum is consistent with a singlet [spin-Peierls (SP)] ground state. At a given pressure, the temperature dependence of the CO order parameter is not monotonic, and provides an opportunity to identify what processes could be controlling the CO amplitude. F-19 NMR spectroscopy provides empirical evidence that electron-counterion coupling is crucial to stabilizing the CO and AF phases.