Abstract
We report thermopower (S) and electrical resistivity (ρ 2DES ) measurements in low-density (1014 m−2), mesoscopic two-dimensional electron systems (2DESs) in GaAs/AlGaAs heterostructures at sub-Kelvin temperatures. We observe at temperatures ≲0.7 K a linearly growing S as a function of temperature indicating metal-like behaviour. Interestingly this metallicity is not Drude-like, showing several unusual characteristics: (i) the magnitude of S exceeds the Mott prediction valid for non-interacting metallic 2DESs at similar carrier densities by over two orders of magnitude; and (ii) ρ 2DES in this regime is two orders of magnitude greater than the quantum of resistance h/e 2 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, ρ 2DES and S show an intriguing decoupling in their density-dependence, the latter showing striking oscillations and even sign changes that are completely absent in the resistivity.
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Acknowledgements
We acknowledge funding from the UK-India Education and Research Initiative (UKIERI), the Department of Science and Technology (DST), India and the Engineering and Physical Sciences Research Council (EPSRC), UK. VN acknowledges a Fellowship from the Herchel Smith Fund.
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Narayan, V., Pepper, M., Griffths, J. et al. Evidence of Novel Quasiparticles in a Strongly Interacting Two-Dimensional Electron System: Giant Thermopower and Metallic Behaviour. J Low Temp Phys 171, 626–631 (2013). https://doi.org/10.1007/s10909-012-0718-0
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DOI: https://doi.org/10.1007/s10909-012-0718-0