Quantum Thermodynamics & Transport
Quantum Thermodynamics & Transport
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Our research in quantum thermodynamics & transport delves into the realm where quantum mechanics intersects with the principles of thermodynamics and the mechanisms of particle or energy transport. At the quantum scale, both the thermodynamic and transport properties undergo modifications due to quantum effects. Phenomena like energy quantization, quantum coherence, correlations, and entanglement can be harnessed to enhance the efficiency of quantum thermodynamic devices. Our research endeavors encompass developing novel quantum-thermodynamic cycles and heat machines, designing cutting-edge quantum devices, and probing into quantum chaos and non-thermalizing systems.
Quantum shape effect
Quantum size and shape effects constitute the backbone of nanoscience and nanotechnology. They are the direct consequences of energy quantization, which is a quintessential characteristic of quantum systems. While quantum size and shape effects are thought to be of similar mechanism and not quite separable, we showed that it is possible to separate the influences of quantum size and shape effects and more importantly quantum shape effect cause quite different, in fact opposite, influence on the system. We introduced the concept of pure quantum shape effect, which can be realized in core-shell nanostructures. We proposed an analytical method which predicts the shape-dependent thermodynamic properties and explain the underlying physical mechanisms of the quantum shape effect. We introduced the isoformal (shape-preserving) process and designed a heat engine cycle driven by quantum shape effects and operating at nanoscale, which exhibits novel thermodynamic behaviors never seen in classical thermodynamics.
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Quantum Shape Effects, Ph.D. Thesis (2020)
Phys. Rev. E, 108, 024105, (2023)
Phys. Rev. E, 107, 054108, (2023)
J. Phys.: Condens. Matter, 34, 025301, (2021)
Phys. Lett. A, 383, 655-665 (2019)
Featured videos:
Nonuniform level scaling and quantum thermal avalanche
Quantum shape effect causes peculiar thermodynamic behaviors such as spontaneous transitions into lower entropy states and cooling (heating) by adiabatic compression (expansion). The underlying physical reason for such classically impossible behaviors lies in the spectra of confined systems. Geometric couplings between levels generated by the size-invariant transformations cause nonuniform scaling of energy levels. In particular, we discovered that a geometry-induced eigenstate swapping occurs due to the shrinkage of the eigenfunctions leading to an excessive occupation of the ground-state, which we call quantum thermal avalanche. Unusual spectral characteristics of size-preserving transformations can assist in designing confinement geometries that could lead to classically inconceivable quantum thermal machines!
Read more:
Phys. Rev. E, 107, 054108, (2023)
Featured videos:
Implications of Nonuniform Level Scaling for Quantum Energy Devices (YouTube)
Hearing the shapes of size-invariant quantum wells (YouTube)
Landauer's principle and demonless Szilard engines
A Szilard engine is basically a thought experiment which has many seemingly counter-intuitive thermodynamic consequences. We proposed a Szilard engine setup without featuring an explicit Maxwell's demon and showed that the heat dissipation occurs inevitably to extract work from the system even if the which-side information is not acquired. We showed that localization by quantum measurement corresponds to a logically irreversible operation which has to be accompanied by the heat dissipation due to the Landauer’s principle, showing the validity of Landauer’s principle in demonless quantum Szilard engines.
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Thermodynamics of quantum-confined nanostructures
Reducing the sizes of the materials to the order of the thermal de Broglie wavelengths of particles causes energy level spacings to increase, making the discrete energy levels to reveal themselves. In strongly confined systems, thermal energy can only excite a few lower-energy levels. Information about the confinement geometry becomes imprinted on the energy spectra. Thermodynamic and transport properties of confined charge carriers in semiconductors or metals are modified due to this confinement, leading to size-dependent quantum-mechanical phenomena that are unseen at the macroscale. Quantum confinement makes discrete energy spectra to prominently reveal itself and, as a result, physical properties such as electronic, phononic, magnetic, mechanical, optical, thermal, thermodynamic, thermoelectric, and superconducting properties of materials become size dependent at nanoscale. As a result, we have discovered many interesting phenomena like dimensional transitions, discrete and oscillatory behaviors in thermodynamic properties of Fermionic systems and geometry-dependent physical properties in general.
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Phys. Lett. A, 382, 1813-1817, (2018)
Phys. Lett. A, 382, 1807-1812, (2018)
Developing analytical methods for the statistical mechanics of confined systems
For a better analysis of the physics of the quantum effects appearing at nanoscale systems, the development of new mathematical tools and methods is needed. We have developed many analytical frameworks, such as discrete density of states, half-vicinity model, overlapped quantum boundary layer method, to predict quantum confinement effects. Some of these frameworks are built upon other already existing concepts, e.g. quantum boundary layer concept. Accurate analytical tools and expressions we have developed make it easier to study such systems.
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Mod. Phys. Lett. B, 32, 1850393, (2018)
Phys. Lett. A, 382, 1813-1817, (2018)
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