A PROPOSAL FOR THE MECHANISMS OF 2 ANOMALOUS PHASE-TRANSITIONS IN HIGH MAGNETIC-FIELDS - SEMIMETALS AND HIGH-TC SUPERCONDUCTORS

For two different kinds of phase transitions under high magnetic fields, tentative mechanisms are proposed. One is a second-order phase transition-like anomaly in the ultrasonic attenuation coefficient versus temperature curve in bismuth, which was observed only when some electron and hole Landau levels simultaneously absorb phonons. In contrast to previous research, this anomaly is interpreted on the basis of Prigogine's nonequilibrium thermodynamic theory. The other is the mechanism of anomalous superconducting transition behavior in resistivity, specific heat and sound velocity in high- Tc superconductors (HTSC) under high magnetic fields. Taking account of the very short coherence length in HTSC, a phenomenological model is proposed of the superconducting transition under magnetic fields, which fits well with the above phenomena, in particular, with a resistive transition under magnetic fields. © 1990, Taylor & Francis Group, LLC. All rights reserved.