Absence of an insulator-metal transition in Rb4C60 up to 2 GPa
2008 (English)In: Physical Review B, ISSN 0163-1829, Vol. 77, no 8, 085434- p.Article in journal (Refereed) Published
We present the results of direct resistance measurements on Rb4C60 under pressures up to 2 GPa. At all pressures covered by this study and over the temperature range of 90–450 K Rb4C60 is a semiconductor with a weakly pressure dependent band gap near 0.7 eV. We do not observe the insulator-to-metal transition previously reported to occur below 1.2 GPa, although we cannot rule out the possibility that such a transition might occur at some significantly higher pressure. The measured resistivity is surprisingly low and is dominated by carriers excited over a 0.1 eV gap. Because the corresponding conductivity increases with deformation of the sample, we assign these states to structural or orientational defects. The known structural transformation below 0.5 GPa leads to a decrease in resistivity under high pressure, but the material remains semiconducting. A Rb6C60 control sample showed a similar behavior, also being a semiconductor under all conditions studied. At temperatures above 460 K, Rb was partially lost from our samples, resulting in metallization by a transformation into Rb3C60.
Place, publisher, year, edition, pages
2008. Vol. 77, no 8, 085434- p.
Fullerene, C60, fulleride, Rb3C60, Rb4C60, Rb6C60, high pressure, metal-insulator transition, phase transition, resistance, conductance, semiconductor, band gap, gap states, superconductivity, critical temperature, Raman spectroscopy, X-ray diffraction, susceptibility, NMR
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:umu:diva-9111DOI: 10.1103/PhysRevB.77.085434OAI: oai:DiVA.org:umu-9111DiVA: diva2:148782
Also selected for the Virtual Journal of Nanoscale Science & Technology, volume 17, issue 11 (March 17, 2008).2008-03-172008-03-172015-09-28Bibliographically approved