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Published on: August 2, 2019
Molecular wires acting as quantum heat ratchets
Fei Zhan1, Nianbei Li, Sigmund Kohler
1Institut für Physik, Universität Augsburg, Universitätsstr 1, D-86135 Augsburg, Germany. fei.zhan@physik.uni-augsburg.de
Summary
Researchers demonstrate a "ratchet effect" in molecular junctions, generating directed heat currents without a net thermal bias using temperature modulation. This effect also produces electric currents and a unique "ratchet Seebeck effect."
Area of Science:
- Condensed matter physics
- Quantum thermodynamics
- Nanoscale heat transfer
Background:
- Heat transfer in nanoscale systems is crucial for device performance.
- Molecular junctions offer a platform to study fundamental transport phenomena.
- Generating directed currents without a net bias is a key challenge in thermodynamics.
Purpose of the Study:
- To investigate heat transfer in molecular junctions under unbiased, time-periodic temperature modulation.
- To explore the emergence of directed heat currents (ratchet effect) via dynamical symmetry breaking.
- To analyze the generation of electric currents and thermopower from modulated heat flow.
Main Methods:
- Theoretical modeling of heat transfer in molecular junctions.
- Applying unbiased, time-periodic temperature modulation to the leads.
- Considering two scenarios: single-lead modulation and dual-lead modulation with harmonic mixing.
- Analyzing heat current-thermal load characteristics and electric current generation.
Main Results:
- Sizable directed heat currents are generated in both modulation scenarios.
- A ratchet effect is observed, enabling heat flow against a negative thermal bias.
- The ratchet heat flow induces an electric current, leading to a "ratchet Seebeck effect."
- The relative phase in harmonic mixing allows steering of the heat current direction.
Conclusions:
- Unbiased temperature modulation can induce directed heat and electric currents in molecular junctions.
- The ratchet effect and associated phenomena are observable with current experimental techniques.
- This work opens possibilities for novel thermoelectric devices and thermal management strategies.
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