The myth of second sound in strontium titanate Original Research Article

SrTiO3 displays near 37 and 65 K a number of different anomalies, reported as early as 1961. In the past decade some additional phenomena have been discovered and interpreted [B. Hehlen, E. Courtens, R. Vacher, Phys. Rev. Lett., 75 (1995) 2416] as second sound, following the initial prediction [V.L. Gurevich, A.K. Tagantsev, Sov. Phys. JETP, 67 (1988) 206] that such heat propagation could occur in this material. The present review of data combines early work and very recent unpublished data to show that such a thesis is not supported by experiment, nor is the suggestion by Mueller et al. that strontium titanate below 37 K exhibits some kind of macroscopic coherence.