Abstract
Full text: Ratchets are non-equilibrium systems in which directed particle motion is generated using spatial or temporal asymmetry. 'Brownian' heat engines are ratchets in which the particles do work against an external force. Brownian heat engines operating in the over-damped regime of transport can generally not reach Carnot efficiency. Here we show that in the ballistic regime Carnot efficient Brownian heat engines are possible. A Landauer based model is used to demonstrate that a heat engine working arbitrarily close to Carnot efficiency may be constructed from two electron reservoirs at different potentials and temperatures, if an energy filter for electrons (such as a quantum dot) is used to restrict transport between the reservoirs to a narrow energy range around the energy where the Fermi distribution functions cross. We apply this result to quantum dot refrigerators and quantum ratchet heat engines, showing that in both cases the limiting efficiency is Carnot efficiency. Carnot efficiency may only be obtained if a device works reversibly. If two reservoirs are at the same temperature but the left reservoir is at a higher potential energy, the difference in potential from left to right will cause an electron current in that direction, cooling the left reservoir
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Humphrey, T;
Newbury, R;
[1]
Linke, H
[2]
- University of New South Wales, Sydney, NSW (Australia). School of Physics
- University of Oregon, (United States). Physics Department
Citation Formats
Humphrey, T, Newbury, R, and Linke, H.
Quantum heat engines with carnot efficiency.
Australia: N. p.,
2002.
Web.
Humphrey, T, Newbury, R, & Linke, H.
Quantum heat engines with carnot efficiency.
Australia.
Humphrey, T, Newbury, R, and Linke, H.
2002.
"Quantum heat engines with carnot efficiency."
Australia.
@misc{etde_20619854,
title = {Quantum heat engines with carnot efficiency}
author = {Humphrey, T, Newbury, R, and Linke, H}
abstractNote = {Full text: Ratchets are non-equilibrium systems in which directed particle motion is generated using spatial or temporal asymmetry. 'Brownian' heat engines are ratchets in which the particles do work against an external force. Brownian heat engines operating in the over-damped regime of transport can generally not reach Carnot efficiency. Here we show that in the ballistic regime Carnot efficient Brownian heat engines are possible. A Landauer based model is used to demonstrate that a heat engine working arbitrarily close to Carnot efficiency may be constructed from two electron reservoirs at different potentials and temperatures, if an energy filter for electrons (such as a quantum dot) is used to restrict transport between the reservoirs to a narrow energy range around the energy where the Fermi distribution functions cross. We apply this result to quantum dot refrigerators and quantum ratchet heat engines, showing that in both cases the limiting efficiency is Carnot efficiency. Carnot efficiency may only be obtained if a device works reversibly. If two reservoirs are at the same temperature but the left reservoir is at a higher potential energy, the difference in potential from left to right will cause an electron current in that direction, cooling the left reservoir (the Peltier effect), and causing heating and irreversible dissipation in the right reservoir. If the two reservoirs are at the same potential, but with different temperatures heat will flow irreversibly from hot to cold and a current of electrons is produced if transport is blocked at lower energies (Seebeck effect). By combining a temperature and potential differential, reversible transfer is possible at the energy at which the occupation functions cross. Below this energy electrons produce an increase in entropy in the system by following the potential gradient from left to right; above this energy electrons follow the thermal gradient from right to left.}
place = {Australia}
year = {2002}
month = {Jul}
}
title = {Quantum heat engines with carnot efficiency}
author = {Humphrey, T, Newbury, R, and Linke, H}
abstractNote = {Full text: Ratchets are non-equilibrium systems in which directed particle motion is generated using spatial or temporal asymmetry. 'Brownian' heat engines are ratchets in which the particles do work against an external force. Brownian heat engines operating in the over-damped regime of transport can generally not reach Carnot efficiency. Here we show that in the ballistic regime Carnot efficient Brownian heat engines are possible. A Landauer based model is used to demonstrate that a heat engine working arbitrarily close to Carnot efficiency may be constructed from two electron reservoirs at different potentials and temperatures, if an energy filter for electrons (such as a quantum dot) is used to restrict transport between the reservoirs to a narrow energy range around the energy where the Fermi distribution functions cross. We apply this result to quantum dot refrigerators and quantum ratchet heat engines, showing that in both cases the limiting efficiency is Carnot efficiency. Carnot efficiency may only be obtained if a device works reversibly. If two reservoirs are at the same temperature but the left reservoir is at a higher potential energy, the difference in potential from left to right will cause an electron current in that direction, cooling the left reservoir (the Peltier effect), and causing heating and irreversible dissipation in the right reservoir. If the two reservoirs are at the same potential, but with different temperatures heat will flow irreversibly from hot to cold and a current of electrons is produced if transport is blocked at lower energies (Seebeck effect). By combining a temperature and potential differential, reversible transfer is possible at the energy at which the occupation functions cross. Below this energy electrons produce an increase in entropy in the system by following the potential gradient from left to right; above this energy electrons follow the thermal gradient from right to left.}
place = {Australia}
year = {2002}
month = {Jul}
}