Article

Anomalous Coulomb diamonds and power-law behavior sensitive to back-gate voltages in carbon nanoscale peapod quantum dots

Physical review. B, Condensed matter (Impact Factor: 3.77). 01/2007; DOI: 10.1103/PhysRevB.75.205431
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ABSTRACT We report anomalous charging effect of single electrons (Coulomb diamonds) observed in carbon nanoscale peapod quantum dots that encapsulate a series of C60 molecules. We find that behaviors of diamonds are anomalously sensitive to back-gate voltages (V_bg), exhibiting two evidently different V_bg regions and a large polarity on V_bg. In particular, we find only a sequence of one large diamond followed by three smaller ones existing around ground state. Magnetic-field dependence indicates the presence of shell filling by spin singlet to doubly degenerate electronic levels for these. The encapsulated-C60 molecules indirectly affect this shell filling at low V_bg possibly via nearly free electrons. In contrast, they act as individual quantum dots coupled in series in high V_bg region. It directly contributes to highly overlapped very large diamonds. Moreover, we report power-law behaviors on conductance versus energy relationships observed in the same carbon nanoscale peapods. We find that the values of powers are also highly sensitive to applied V_bg with three different regions and anomalously high at high source-drain voltages. Because the power laws are found at voltages, which are the nearest outside of the above-mentioned fourfold Coulomb diamonds, correlation of the anomalous powers with orbital-related Tomonaga-Luttinger liquid is discussed. PHYSICAL REVIEW B. v.75, n.20, 2007, p.205431-1-205431-7

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May 31, 2014