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Highly enhanced thermopower in two-dimensional electron systems at millikelvin temperatures
Srijit Goswami1, Christoph Siegert, Matthias Baenninger
1Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom. sg483@cam.ac.uk
Physical Review Letters
|August 8, 2009
Summary
Researchers observed a large thermopower in two-dimensional (2D) electron systems at very low temperatures. This unexpected phenomenon, exceeding free electron estimates, may stem from localized states and spin correlations.
Area of Science:
- Condensed Matter Physics
- Mesoscopic Physics
- Semiconductor Heterostructures
Background:
- Two-dimensional (2D) electron systems in semiconductor heterostructures are crucial for understanding electron transport phenomena.
- Conventional thermopower in nonmagnetic, high-mobility 2D systems typically decreases with temperature.
- Sub-Kelvin temperatures offer a unique regime to probe exotic electronic behaviors.
Purpose of the Study:
- To experimentally investigate the thermopower behavior in mesoscopic 2D electron systems at sub-Kelvin temperatures.
- To explore deviations from conventional thermopower predictions in GaAs/AlGaAs heterostructures.
- To identify potential mechanisms behind unexpectedly large thermopower values.
Main Methods:
- Experimental measurements of thermopower in GaAs/AlGaAs heterostructures.
- Utilizing sub-Kelvin cryogenic temperatures and zero magnetic field conditions.
- Conducting parallel studies of the local density of states.
Main Results:
- Observed an unexpectedly large thermopower, exceeding 100 microV/K, at temperatures below 0.3 K.
- Thermopower increased with decreasing temperature, contrary to conventional behavior.
- The observed thermopower was more than two orders of magnitude larger than the free electron estimate.
Conclusions:
- The large thermopower is linked to intrinsic localized states within the 2D electron system.
- Many-body spin correlations are suggested as a contributing factor to the enhanced thermopower.
- These findings open new avenues for exploring quantum phenomena in mesoscopic systems.
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