Glass transition in the spin-density wave phase of (TMTSF)2PF6

We present the results of low frequency dielectric measurements and a detailed kinetic investigation of the specific heat anomaly in the spin-density wave phase of (TMTSF${)}_2$ ${\mathrm{PF}}_6$ in the temperature range between 2 and 4 K. The dielectric relaxation shows a critical slowing down towards a ‘‘static’’glass transition around 2 K. The jump in the specific heat in different controlled kinetic conditions shows all the characteristics of freezing in supercooled liquids. Both effects give direct evidence of a glass transition in the spin-density wave ground state.