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Absence of an insul...
Abstract
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- 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.
Subject headings
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
Keyword
- 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
- Kondenserade materiens fysik
Publication and Content Type
- ref (subject category)
- art (subject category)
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