1 entropy and the laws of thermodynamics 1 1.1 Entropy 2 1.1.1Classical and Statistical Entropy 4 1.1.2Aspects of Entropy 6 1.2 The 0th Law 7 1.3The 1st Law 7 1.4The 2nd Law 8 2 the third law 11 2.1 Consequences of the Third Law 12 2.2 Helium and the Third Law 14 2.3 Non-Equilibrium Degrees of Freedom 15 2.4 The Unattainability of Absolute Zero 19 3 violations of the laws of thermodynamics 23 3.1 The Second Law 23 3.1.1Fluctuations 24 3.2 The Third Law 26 4 the boson driven refrigerator 29 4.1 Introduction of the Refrigerator Model 29 4.2 Discussion 30 4.3 Non-Equilibrium Systems and Thermodynamics 36 4.4 Objective 37 5 non-equilibrium thermodynamics 39 5.1 The Stochastic Master Equation 40 5.2 Local Detailed Balance 41 5.3 The Stochastic Laws of Thermodynamics 42 5.3.1 The First Law 42 5.3.2The Second Law 43 5.4 Tight Coupling and Efficiency 45 6 boson powered refrigeration 49 6.1 Particle Currents 49 6.2 Heat Transport and Effieciency 52 6.3 Cooling power in the Limit of Absolute Zero 56 7 numerically optimized cooling 59 7.1 Conditions for Optimized Cooling 59 7.2 The Very Low Temperature Regime 63 8 finite energy level spacing 67 8.1 Dependency on δ and ∆ 73 8.2 Maximized Cooling Power 75 8.3 Higher Order Transitions 79 VII VIII contents 8.4 Heat Capacity of the Discrete Model 80 8.5 The Unattainability of Absolute Zero 82 9 summary 85 9.1 Summary and Conclusions 85 9.2 Discussion 86 9.3 Recommendations for Further Work 87 a appendix 89 a.1 C++ Source Code for the Continuous Model 89 a.2 C++ Source Code for the Discrete Model 96
1 entropy and the laws of thermodynamics 1 1.1 Entropy 2 1.1.1Classical and Statistical Entropy 4 1.1.2Aspects of Entropy 6 1.2 The 0th Law 7 1.3The 1st Law 7 1.4The 2nd Law 8 2 the third law 11 2.1 Consequences of the Third Law 12 2.2 Helium and the Third Law 14 2.3 Non-Equilibrium Degrees of Freedom 15 2.4 The Unattainability of Absolute Zero 19 3 violations of the laws of thermodynamics 23 3.1 The Second Law 23 3.1.1Fluctuations 24 3.2 The Third Law 26 4 the boson driven refrigerator 29 4.1 Introduction of the Refrigerator Model 29 4.2 Discussion 30 4.3 Non-Equilibrium Systems and Thermodynamics 36 4.4 Objective 37 5 non-equilibrium thermodynamics 39 5.1 The Stochastic Master Equation 40 5.2 Local Detailed Balance 41 5.3 The Stochastic Laws of Thermodynamics 42 5.3.1 The First Law 42 5.3.2The Second Law 43 5.4 Tight Coupling and Efficiency 45 6 boson powered refrigeration 49 6.1 Particle Currents 49 6.2 Heat Transport and Effieciency 52 6.3 Cooling power in the Limit of Absolute Zero 56 7 numerically optimized cooling 59 7.1 Conditions for Optimized Cooling 59 7.2 The Very Low Temperature Regime 63 8 finite energy level spacing 67 8.1 Dependency on δ and ∆ 73 8.2 Maximized Cooling Power 75 8.3 Higher Order Transitions 79 VII VIII contents 8.4 Heat Capacity of the Discrete Model 80 8.5 The Unattainability of Absolute Zero 82 9 summary 85 9.1 Summary and Conclusions 85 9.2 Discussion 86 9.3 Recommendations for Further Work 87 a appendix 89 a.1 C++ Source Code for the Continuous Model 89 a.2 C++ Source Code for the Discrete Model 96
The second and third laws of thermodynamics can be used to establish a fundamental bound for the maximum possible cooling rate in approaching the absolute zero of temperature. In modeling the behavior of the molecular refrigerators geared toward attaining ultralow temperatures, only quantum mechanical, as opposed to classical physics, models can be admissible. As a simple model, we analyze a three-level quantum refrigerator, and in particular its irreversible thermodynamic performance as absolute zero is approached.
Introduction In most of the discussion presented so far in this book, the quantum character of atoms and electrons has been ignored. The Ising spin models have been an exception, but since the Ising Hamiltonian is diagonal (in the absence of a transverse magnetic field), all energy eigenvalues are known and the Monte Carlo sampling can be carried out just as in the case of classical statistical mechanics. Furthermore, the physical properties are in accord with the third law of thermodynamics for Ising-type Hamiltonians (e.g. entropy S and specific heat vanish for temperature T → 0, etc.) in contrast to the other truly classical models dealt with in previous chapters (e.g. classical Heisenberg spin models, classical fluids and solids, etc.) which have many unphysical low temperature properties. A case in point is a classical solid for which the specific heat follows the Dulong–Petit law, C = 3 Nk B , as T → 0, and the entropy has unphysical behavior since S → –∞. Also, thermal expansion coefficients tend to non-vanishing constants for T → 0 while the third law implies that they must be zero. While the position and momentum of a particle can be specified precisely in classical mechanics, and hence the groundstate of a solid is a perfectly rigid crystal lattice (motionless particles localized at the lattice points), in reality the Heisenberg uncertainty principle forbids such a perfect rigid crystal, even at T → 0, due to zero point motions which ‘smear out’ the particles over some region around these lattice points. This delocalization of quantum-mechanical particles increases as the atomic mass is reduced; therefore, these quantum effects are most pronounced for light atoms like hydrogen in metals, or liquid helium. Spectacular phenomena like superfluidity are a consequence of the quantum nature of the particles and have no classical counterpart at all. Even for heavier atoms, which do not show superfluidity because the fluid–solid transition intervenes before a transition from normal fluid to superfluid could occur, there are genuine effects of quantum nature. Examples include the isotope effects (remember that in classical statistical mechanics the kinetic energy part of the Boltzmann factor cancels out from all averages, and thus in thermal equilibrium no property depends explicitly on the mass of the particles).
The emergence of the laws of thermodynamics from the laws of quantum mechanics is an unresolved issue. The generation of the third law of thermodynamics from quantum dynamics is analysed. The scaling of the optimal cooling power of a reciprocating quantum refrigerator is sought as a function of the cold bath temperature as T c →0. The working medium consists of noninteracting particles in a harmonic potential. Two closed-form solutions of the refrigeration cycle are analyzed, and compared to a numerical optimization scheme, focusing on cooling toward zero temperature. The optimal cycle is characterized by linear relations between the heat extracted from the cold bath, the energy level spacing of the working medium and the temperature. The scaling of the optimal cooling rate is found to be proportional to T c 3/2 giving a dynamical interpretation to the third law of thermodynamics.
Commentaries.- A Survey by the Editors.- I. Thermodynamic Limit for Coulomb Systems.- I. 1 Existence of Thermodynamics for Real Matter with Coulomb Forces.- I. 2 The Constitution of Matter: Existence of Thermodynamics for Systems Composed of Electrons and Nuclei.- II. Hard Sphere Virial Coefficients.- II. 1 Suppression at High Temperature of Effects Due to Statistics in the Second Virial Coefficient of a Real Gas.- II. 2 Calculation of Exchange Second Virial Coefficient of a Hard-Sphere Gas by Path Integrals.- III. Zeros of Partition Functions.- III. 1 Monomers and Dimers.- III. 2 Theory of Monomer-Dimer Systems.- III. 3 A Property of Zeros of the Partition Function for Ising Spin Systems.- III. 4 A General Lee-Yang Theorem for One-Component and Multicomponent Ferromagnets.- IV. Reflection Positivity.- IV. 1 Existence of Phase Transitions for Anisotropic Heisenberg Models.- IV. 2 Phase Transitions in Anisotropic Lattice Spin Systems.- IV. 3 Phase Transitions in Quantum Spin Systems with Isotropic and Nonisotropic Interactions.- IV. 4 Phase Transitions and Reflection Positivity. I. General Theory and Long Range Lattice Models.- IV. 5 Phase Transitions and Reflection Positivity. II. Lattice Systems with Short-Range and Coulomb Interactions.- IV. 6 Lattice Models for Liquid Crystals.- IV. 7 Existence of Neel Order in Some Spin-1/2 Heisenberg Antiferromagnets.- IV. 8 The XY Model Has Long-Range Order for all Spins and all Dimensions Greater than One.- V. Classical Thermodynamics.- V. 1 The Third Law of Thermodynamics and the Degeneracy of the Ground State for Lattice Systems.- V. 2 A Guide to Entropy and the Second Law of Thermodynamics.- V. 3 A Fresh Look at Entropy and the Second Law of Thermodynamics.- VI. Lattice Systems.- VI. 1 Properties of a Harmonic Crystal in a Stationary Nonequilibrium State.- VI. 2 The Statistical Mechanics of Anharmonic Lattices.- VI. 3 Time Evolution of Infinite Anharmonic Systems.- VI. 4 Lattice Systems with a Continuous Symmetry III. Low Temperature Asymptotic Expansion for the Plane Rotator Model.- VII. Miscellaneous.- VII. 1 The Finite Group Velocity of Quantum Spin Systems.- VII. 2 The Classical Limit of Quantum Spin Systems.- VII. 3 A Refinement of Simon's Correlation Inequality.- VII. 4 Fluxes, Laplacians, and Kasteleyn's Theorem.- Selecta of Elliott H. Lieb.- Publications of Elliott H. Lieb.
1 Introduction 52 Equilibrium statistical mechanics 72.1 Basics; correlation functions . . 72.2 Externalfield;linearresponse 82.3 Continuous systems: functional integral . . . 112.4 Examples:elasticsystems 173 Calculation of Functional Integrals 293.1 Perturbationtheory 293.2 Variationalmethod 313.3 Saddlepointmethod 324 Quantum problems; functional integral 354.1 Singleparticle 354.2 Correlation functions; Matsubara frequencies 394.3 Many degrees of freedom: example of the elastic system . . 424.4 Linkwithclassicalproblems 445 Perturbation; Linear response 475.1 Method 475.2 Analyticalcontinuation 505.3 Fluctuationdissipationtheorem 525.4 Kuboformula 535.5 Scattering, Memory function . 576 Examples 596.1 Compressibility . 596.2 Conductivity of quantum crystals; Hall effect 616.3 Commensuratesystems 667 Out of equilibrium classical systems 697.1 Overdampeddynamics 697.2 Linkwiththermodynamics 707.3 MSRFormalism 723
The rate of temperature decrease of a cooled quantum bath is studied as its temperature is reduced to absolute zero. The third law of thermodynamics is then quantified dynamically by evaluating the characteristic exponent ζ of the cooling process dT(t)/dt∼-T^{ζ} when approaching absolute zero, T→0. A continuous model of a quantum refrigerator is employed consisting of a working medium composed either by two coupled harmonic oscillators or two coupled two-level systems. The refrigerator is a nonlinear device merging three currents from three heat baths: a cold bath to be cooled, a hot bath as an entropy sink, and a driving bath which is the source of cooling power. A heat-driven refrigerator (absorption refrigerator) is compared to a power-driven refrigerator. When optimized, both cases lead to the same exponent ζ, showing a lack of dependence on the form of the working medium and the characteristics of the drivers. The characteristic exponent is therefore determined by the properties of the cold reservoir and its interaction with the system. Two generic heat bath models are considered: a bath composed of harmonic oscillators and a bath composed of ideal Bose/Fermi gas. The restrictions on the interaction Hamiltonian imposed by the third law are discussed. In the Appendices, the theory of periodically driven open systems and its implication for thermodynamics are outlined.