Multi-dot Aharonov-Bohm Engines Harness Interference for Near-Optimal Power and Efficiency

Harnessing heat for energy represents a significant challenge in developing efficient, low-power technologies, and researchers are now exploring how to control heat flow at the nanoscale. Sridhar, Salil Bedkihal, and Malay Bandyopadhyay, from institutions including the Indian Institute of Technology Bhubaneswar and Dartmouth College, investigate the potential of multi-dot structures to act as highly effective thermoelectric heat engines. Their work demonstrates that carefully engineering the way electrons travel through these nanostructures, by manipulating interference effects, allows for precise control over both the power generated and the efficiency of the engine. The team shows that specific configurations, particularly those with hexagonal arrangements of dots, can achieve remarkable performance, approaching Carnot efficiency and generating measurable power at extremely low temperatures, paving the way for innovative designs in ultralow-power electronics.

The team theoretically investigated how manipulating the electronic transmission functions within these devices, specifically through geometry, magnetic flux, and coupling strengths, allows for a balance between high efficiency and substantial power output. Calculations reveal that tailored transmission profiles, combining features like Lorentzian and boxcar shapes, optimize performance, and a specific coupling regime, where interdot tunneling and dot-lead coupling are balanced, yields the best results.

Notably, a hexagonal six-dot configuration achieves a figure of merit of approximately 30 at very low temperatures, while a four-dot geometry reaches around 76% of Carnot efficiency with a power output of several femtowatts. This demonstrates the potential for substantial improvements in thermoelectric performance through careful design. Scaling analysis indicates that increasing the number of dots generally improves efficiency, although power output peaks at intermediate system sizes, highlighting a trade-off between these two key metrics.

Nanoscale Quantum Transport and Thermoelectricity

This collection of research explores the fundamental principles of quantum transport and their application to nanoscale thermoelectric devices. It focuses on understanding how electrons behave at extremely small scales, where quantum mechanical effects dominate. Key areas of investigation include the behaviour of electrons in quantum dots, nanowires, and molecular junctions, and how these structures can be used to convert temperature differences into electrical energy. The research aims to improve the efficiency of thermoelectric materials for applications in energy harvesting and cooling.

The work delves into several important concepts, including the Aharonov-Bohm effect, where electrons are influenced by electromagnetic potentials even without a magnetic field, and the Dicke effect, which describes the collective interaction of quantum dots with radiation. The research utilizes the Nonequilibrium Green’s Function (NEGF) formalism, a powerful theoretical tool for calculating electronic and thermal transport properties in nanoscale devices. Fundamental principles like the Landauer formula and Onsager relations are applied to relate current and heat flow to electron transmission probabilities.

Researchers are actively exploring strategies to manipulate quantum coherence and interference effects to control electron transport and enhance thermoelectric performance. This includes designing devices with tailored transmission profiles, such as combining sharp resonances with broad, flat bands, to achieve optimal performance. The collection highlights the importance of understanding and controlling these quantum phenomena to create more efficient and powerful nanoscale devices.

Hexagonal Nanostructure Optimizes Thermoelectric Performance

This research demonstrates how careful control of quantum interference in multi-dot nanostructures can significantly enhance the performance of thermoelectric heat engines. The team theoretically investigated how manipulating the electronic transmission functions within these devices, specifically through geometry, magnetic flux, and coupling strengths, allows for a balance between high efficiency and substantial power output. Calculations reveal that tailored transmission profiles, combining features like Lorentzian and boxcar shapes, optimize performance, and a specific coupling regime, where interdot tunneling and dot-lead coupling are balanced, yields the best results.

Notably, a hexagonal six-dot configuration achieves a figure of merit of approximately 30 at very low temperatures, while a four-dot geometry reaches around 76% of Carnot efficiency with a power output of several femtowatts. This demonstrates the potential for substantial improvements in thermoelectric performance through careful design. Scaling analysis indicates that increasing the number of dots generally improves efficiency, although power output peaks at intermediate system sizes, highlighting a trade-off between these two key metrics. Future research directions include experimental validation of these theoretical predictions using semiconductor quantum dots, graphene structures, or molecular junctions, and further exploration of the interplay between system size, efficiency, and power output.