4 research outputs found
Evidence of Novel Quasiparticles in a Strongly Interacting Two-Dimensional Electron System: Giant Thermopower and Metallic Behaviour
We report thermopower () and electrical resistivity ()
measurements in low-density (10 m), mesoscopic two-dimensional
electron systems (2DESs) in GaAs/AlGaAs heterostructures at sub-Kelvin
temperatures. We observe at temperatures 0.7 K a linearly growing
as a function of temperature indicating metal-like behaviour. Interestingly
this metallicity is not Drude-like, showing several unusual characteristics: i)
the magnitude of exceeds the Mott prediction valid for non-interacting
metallic 2DESs at similar carrier densities by over two orders of magnitude;
and ii) in this regime is two orders of magnitude greater than
the quantum of resistance and shows very little temperature-dependence.
We provide evidence suggesting that these observations arise due to the
formation of novel quasiparticles in the 2DES that are not electron-like.
Finally, and show an intriguing decoupling in their
density-dependence, the latter showing striking oscillations and even sign
changes that are completely absent in the resistivity.Comment: QFS2012 Conference proceedings, Journal of Low Temperature Physics,
accepted (figure and discussion added upon referee suggestions
Animal snoRNAs and scaRNAs with exceptional structures
The overwhelming majority of small nucleolar RNAs (snoRNAs) fall into two clearly defined classes characterized by distinctive secondary structures and sequence motifs. A small group of diverse ncRNAs, however, shares the hallmarks of one or both classes of snoRNAs but differs substantially from the norm in some respects. Here, we compile the available information on these exceptional cases, conduct a thorough homology search throughout the available metazoan genomes, provide improved and expanded alignments, and investigate the evolutionary histories of these ncRNA families as well as their mutual relationships