High-pressure Electrical Transport Research Articles

High-pressure electrical transport measurements on p-type GaSe and InSe

We performed high-pressure Hall effect and resistivity measurements in p-type GaSe and InSe up to 12 GPa. The pressure behaviour of the transport parameters shows dramatic differences between both materials. In GaSe, the hole concentration and mobility increase moderately and continuously. In InSe, the hole mobility raises rapidly and the hole concentration increases abruptly near 0.8 GPa. The observed results are attributed to the different pressure evolution of the valence-band structure in each material. In InSe a carrier-type inversion is also detected near 4.5 GPa.

Pressure-Induced Superconductivity in Filled Skutterudite PrRu4P12

The high-pressure and low-temperature electrical transport properties of the filled skutterudite, PrRu 4 P 12 , which exhibits a metal-to-insulator (M–I) transition at 62 K (= T MI ), are studied by electrical resistance measurements up to 15 GPa. With increasing pressure, the temperature dependence of resistance below T MI exhibited a semiconductor-like behavior, which changed to a metallic one above 11 GPa. Moreover, a superconducting transition was observed at approximately 1.8 K and the critical magnetic field was 2 T. This is the first example of pressure-induced superconductivity in filled skutterudite compounds.

High pressure electrical transport measurements of Cs 2MoS 4 and KTbP 2Se 6 and X-ray diffraction study of Cs 2MoS 4

We report the results of electrical resistance measurements at high pressures on Cs 2MoS 4 and KTbP 2Se 6. The results of high pressure X-ray diffraction study of Cs 2MoS 4 are also presented. Interestingly, in the case of Cs 2MoS 4 the resistance vs. pressure follows the behavior of the absorption edge vs. pressure obtained from our optical measurements lending further support to a direct–indirect band crossing. In the case of KTbP 2Se 6,the phase transition at about 9.2 GPa is reflected in a sharp drop of the resistance. In addition we report the pressure dependence of the lattice constants as well as the equation of state of Cs 2MoS 4.

Exploring superconductivity in low-Z materials at megabar pressures

Abstract We have developed high-pressure electrical transport methods and have applied them at record pressures of 260 GPa and at temperatures down to the millikelvin range. These experiments have been crucial for studies of metallization and the search for superconductivity in a number of elemental and simple compounds. Here we discuss recent applications of the techniques to various low-Z materials, including lithium, boron, nitrogen, hydrogen, and decaborane B10H14 at megabar pressures.

Magnetic and high-pressure magnetotransport properties of cesium-substituted lanthanum calcium manganites

The nature of the double-exchange (DE) interaction in lanthanum manganites is studied through chemical substitutions, Cs for La, and high-pressure measurements. Static and high-frequency magnetic measurements and high-pressure electrical transport studies were carried out on bulk polycrystalline and radio-frequency sputtered thin films of La0.7-xCsxCa0.3MnO3 for x=0-0.1. The samples are found to be cubic. Curie temperature Tc measurements provide evidence for bond-length-related weakening of DE as x is increased from 0 to 0.03. For higher x, the bond-angle-related changes lead to an increase in the strength of DE. High-pressure mangetoresistance data indicate both bond length and bond-angle-related increase of 10–20 K/GPa in Tc with pressure, with the largest increase measured for x=0.03. The rate of increase in the Curie temperature with pressure decreases with increasing Tc. Anomalies are observed in the magnetic parameters for x=0.03. The Cs-concentration dependence of the low-temperature saturation magnetization shows a minimum close to x=0.03. Ferromagnetic resonance studies at x-band reveal a 5% decrease in the g-value for x=0.03 relative to the end members (x=0 and 0.1). The low-field magnetostriction for x=0.03 indicates a relatively strong electron–phonon spin coupling compared to neighboring compositions.