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The results of wide-range measurements of the low-frequency, rf, and microwave conductivity in the typical mixed-valent narrow-gap semiconductor samarium hexaboride are presented. The established steplike anomaly of conductivity ͑͒ around 10 GHz is discussed in the framework of the exciton-polaron approach and coherent-state formation in SmB 6 at helium temperatures. A combined analysis of the dc-and wide-range ac-transport characteristics and dielectric permittivity data at low temperatures is developed.

Nearly all glass-forming liquids feature, along with the structural alpha-relaxation process, a faster secondary process (beta relaxation), whose nature belongs to the great mysteries of glass physics. However, for some of these liquids, no well-pronounced secondary relaxation is observed. A prominent example is the archetypical glass-forming liquid glycerol. In the present work, by performing dielectric spectroscopy under superhigh pressures up to 6 GPa, we show that in glycerol a significant secondary relaxation peak appears in the dielectric loss at P>3 GPa. We identify this beta relaxation to be of Johari-Goldstein type and discuss its relation to the excess wing. We provide evidence for a smooth but significant increase in glass-transition temperature and fragility on increasing pressure.

An in situ high-temperature--high-pressure study of liquid chalcogenide AsS by x-ray diffraction, resistivity measurements, and quenching from melt is presented. The obtained data provide direct evidence for the existence in the melt under compression of two transformations: one is from a moderate-viscosity molecular liquid to a high-viscosity nonmetallic polymerized liquid at P approximately 1.6-2.2 GPa; the other is from the latter to a low-viscosity metallic liquid at P approximately 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.