SOLID STATE AND QUANTUM THEORY FOR OPTOELECTRONICS Michael A. Parker Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number: 978-0-8493-3750-5 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the valid- ity of all materials or the consequences of their use. 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TA1750.P3725 2010 621.381’045--dc22 2009030736 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface...........................................................................................................................................xvii Author............................................................................................................................................xix Chapter 1 Introduction tothe Solid State....................................................................................1 1.1 Brief Preview....................................................................................................1 1.2 Introduction to Matter and Bonds....................................................................3 1.2.1 Gassesand Liquids..............................................................................3 1.2.2 Solids...................................................................................................4 1.2.3 Bondingand thePeriodic Table..........................................................5 1.2.4 DopantAtoms......................................................................................8 1.3 Introduction to Bands andTransitions.............................................................9 1.3.1 Intuitive Origin of Bands....................................................................9 1.3.2 IndirectBandsand Light- andHeavy-Hole Bands...........................11 1.3.3 Introduction toTransitions................................................................13 1.3.4 Introduction toBand-Edge Diagrams...............................................14 1.3.5 Bandgap States and Defects..............................................................15 1.4 Introduction to thepn Junction......................................................................16 1.4.1 JunctionTechnology.........................................................................17 1.4.2 Band-Edge Diagramsand the pnJunction........................................18 1.4.3 NonequilibriumStatistics..................................................................19 1.5 DeviceTrends.................................................................................................21 1.5.1 Monolithic Integrationof Device Types...........................................21 1.5.2 Year 2000Benchmarks.....................................................................21 1.5.3 SmallOptical Signals........................................................................22 1.5.4 Fabrication Challenges......................................................................23 1.6 VacuumTubes andTransistors......................................................................23 1.6.1 VacuumTube....................................................................................23 1.6.2 Bipolar Transistor..............................................................................24 1.6.3 Field-Effect Transistor.......................................................................25 1.7 Brief Summaryof Some EarlyNanometer-Scale Devices............................26 1.7.1 Resonant-Tunnel Device...................................................................26 1.7.2 Resonant-Tunneling Transistor.........................................................26 1.7.2.1 Single-Electron Transistors................................................27 1.7.2.2 Quantum Cellular Automation (QCA)..............................27 1.7.2.3 Aharanov–BohmEffect Device.........................................27 1.7.2.4 Quantum Interference Devices..........................................28 1.7.2.5 Josephson Junction............................................................28 1.8 Review Exercises............................................................................................28 References and Further Readings..............................................................................29 Chapter 2 Vector and Hilbert Spaces.........................................................................................31 2.1 Vectorand HilbertSpaces..............................................................................31 2.1.1 Motivation forLinear Algebra inQuantum Theory.........................31 2.1.2 Definition of Vector Space................................................................33 iii iv Contents 2.1.3 Hilbert Space.....................................................................................34 2.1.4 Comment onthe Length ofa Vector forQuantum Theory..............36 2.1.5 Linear Isomorphism...........................................................................37 2.1.6 Antilinear Isomorphism.....................................................................37 2.2 DiracNotation andEuclidean Vector Spaces................................................37 2.2.1 Kets,Bras, and Brackets for Euclidean Space..................................38 2.2.2 Basisand Completeness forEuclidean Space...................................39 2.2.3 Closure Relation for theEuclidean Vector Space.............................40 2.2.4 Euclidean Dual Vector Space............................................................41 2.2.5 Inner Product and Norm....................................................................44 2.3 Introduction to Coordinateand Vector Representation ofFunctions............45 2.3.1 Initial View of theCoordinate Representation ofFunctions............46 2.3.2 Coordinate Basis Set.........................................................................47 2.3.3 Introduction tothe Inner Product forFunctions...............................49 2.3.4 Representationsof Functions............................................................49 2.4 Function Space with Discrete Basis Sets.......................................................50 2.4.1 Introduction toHilbert Space............................................................50 2.4.2 Hilbert Space ofFunctionswithDiscrete Basis Vectors..................51 2.4.3 Closure Relation for Functions with aDiscrete Basis......................53 2.4.4 Norms and Inner Products forFunction Spaces with DiscreteBasisSets....................................................................54 2.4.5 Discussion ofWeightFunctions.......................................................55 2.4.6 SomeMiscellaneous Notes on Notation...........................................58 2.5 Function Spaces with Continuous Basis Sets................................................59 2.5.1 Continuous Basis Setof Functions...................................................59 2.5.2 Coordinate Space...............................................................................61 2.5.3 Representationsof theDiracDelta Using Basis Vectors..................64 2.6 Graham–Schmidt OrthonormalizationProcedure...........................................65 2.6.1 Simplest Case of TwoVectors..........................................................65 2.6.2 More than Two Vectors....................................................................66 2.7 Fourier Basis Sets...........................................................................................66 2.7.1 Fourier Cosine Series........................................................................67 2.7.2 Fourier SineSeries............................................................................68 2.7.3 Fourier Series.....................................................................................69 2.7.4 Alternate Basis for theFourierSeries...............................................71 2.7.5 Fourier Transform..............................................................................71 2.8 Closure Relations,Kronecker Delta,and Dirac Delta Functions...................73 2.8.1 Alternate Closure Relationsand Representations of theKronecker Delta Function forEuclidean Space.....................74 2.8.2 CosineBasis Functions.....................................................................75 2.8.3 Sine Basis Functions.........................................................................77 2.8.4 Fourier Series Basis Functions..........................................................77 2.8.5 SomeNotes........................................................................................78 2.9 Introduction to Direct Product Spaces............................................................79 2.9.1 Overview ofDirect Product Spaces..................................................79 2.9.2 Introduction toDyadicNotation forthe Tensor Product of Two Euclidean Vectors.................................................................82 2.9.3 Direct Product Spacefrom theFourier Series..................................82 2.9.4 Components and Closure Relation fortheDirect Product of Functionswith DiscreteBasisSets...............................................84 2.9.5 Noteson theDirect Productsof Continuous Basis Sets...................85 Contents v 2.10 Introduction to MinkowskiSpace..................................................................86 2.10.1 Coordinates andPseudo-Inner Product.............................................86 2.10.2 Pseudo-Orthogonal Vector Notation.................................................86 2.10.3 TensorNotation.................................................................................86 2.10.4 Derivatives.........................................................................................87 2.11 Brief Discussionof Probability andVectorComponents..............................88 2.11.1 Simple2-D Space forStarters...........................................................88 2.11.2 Introduction toApplications ofthe Probability................................90 2.11.3 Discrete and Continuous HilbertSpaces...........................................91 2.11.4 Contrast with RandomVectors.........................................................92 2.12 Review Exercises............................................................................................92 References and Further Readings..............................................................................98 Chapter 3 Operators andHilbert Space.....................................................................................99 3.1 Introduction to Operatorsand Groups............................................................99 3.1.1 Linear Operator...............................................................................100 3.1.2 Transformations of theBasis Vectors Determine the Linear Operator.........................................................................100 3.1.3 Introduction toIsomorphisms.........................................................101 3.1.4 Comments on Groupsand Operators..............................................101 3.1.5 Permutation Group and a Matrix Representation: An Example.....................................................................................103 3.2 MatrixRepresentations.................................................................................104 3.2.1 Definition of Matrix for an Operator withIdentical Domain and RangeSpaces............................................................................105 3.2.2 Matrixof an Operator withDistinctDomain and RangeSpaces............................................................................106 3.2.3 Dirac Notation forMatrices............................................................107 3.2.4 Operating on anArbitrary Vector...................................................109 3.2.5 MatrixEquation...............................................................................110 3.2.6 Matrices for Function Spaces..........................................................113 3.2.7 Introduction toOperator Expectation Values..................................114 3.2.8 MatrixNotation forAverages.........................................................115 3.3 Common Matrix Operations.........................................................................116 3.3.1 Composition of Operators...............................................................116 3.3.2 Isomorphism between Operatorsand Matrices...............................117 3.3.3 Determinant.....................................................................................118 3.3.4 Introduction tothe Inverseof an Operator......................................120 3.3.5 Trace................................................................................................122 3.3.6 Transpose and Hermitian Conjugate ofa Matrix............................123 3.4 Operator Space.............................................................................................124 3.4.1 Concepts and SectionSummary......................................................124 3.4.2 BasisExpansion ofa Linear Operator............................................126 3.4.3 Introduction tothe Inner Product fora HilbertSpace of Operators.....................................................................................129 3.4.4 Proof of theInner Product...............................................................131 3.4.5 BasisforMatrices............................................................................132 3.5 Operators and Matrices inDirect Product Space.........................................133 3.5.1 Review ofDirect Product Spaces....................................................133 3.5.2 Operators.........................................................................................134 vi Contents 3.5.3 Matrices of Direct Product Operators.............................................134 3.5.4 MatrixRepresentationof Basis Vectors for Direct Product Space.................................................................137 3.6 Commutatorsand Algebra ofOperators......................................................138 3.6.1 Initial Discussionof Operator Algebra...........................................139 3.6.2 Introduction toCommutators..........................................................140 3.6.3 SomeCommutator Theorems..........................................................141 3.7 Unitary Operators andSimilarity Transformations......................................143 3.7.1 OrthogonalRotation Matrices.........................................................143 3.7.2 Unitary Transformations..................................................................146 3.7.3 VisualizingUnitary Transformations..............................................147 3.7.4 Traceand Determinant....................................................................148 3.7.5 Similarity Transformations..............................................................148 3.7.6 Equivalent andReducible Representations of Groups....................150 3.8 Hermitian Operators and theEigenvector Equation.....................................151 3.8.1 Adjoint, Self-Adjoint, and Hermitian Operators.............................152 3.8.2 Adjoint and Self-Adjoint Matrices..................................................154 3.9 Relation between Unitaryand Hermitian Operators....................................156 3.9.1 Relation between Hermitian andUnitary Operators.......................156 3.10 Eigenvectors and Eigenvaluesfor Hermitian Operators..............................158 3.10.1 BasicTheorems forHermitian Operators.......................................158 3.10.2 Direct Product Space.......................................................................162 3.11 Eigenvectors, Eigenvalues,and DiagonalMatrices.....................................162 3.11.1 Motivation forDiagonal Matrices...................................................162 3.11.2 Eigenvectors andEigenvalues.........................................................164 3.11.3 Diagonalize a Matrix.......................................................................165 3.11.4 Relation between aDiagonal Operator and the Change-of-Basis Operator..................................................169 3.12 Theorems forHermitian Operators...............................................................170 3.12.1 Common Theorems.........................................................................171 3.12.2 Bounded Hermitian OperatorsHave Complete Sets of Eigenvectors................................................................................172 3.12.3 Derivation ofthe Heisenberg Uncertainty Relation........................176 3.13 Raising–Loweringand Creation–Annihilation Operators............................179 3.13.1 Definition of theLadder Operators.................................................179 3.13.2 Matrixand Basis-Vector Representations ofthe Raising and LoweringOperators..................................................................180 3.13.3 Raising and Lowering Operatorsfor Direct Product Space............182 3.14 Translation Operators...................................................................................183 3.14.1 Exponential Form of theTranslation Operator...............................183 3.14.2 Translation of thePosition Operator...............................................184 3.14.3 Translation of thePosition-CoordinateKet....................................185 3.14.4 Example Using theDirac Delta Function.......................................185 3.14.5 Relation among HilbertSpaceand the 1-D Translation, and Lie Group.................................................................................186 3.14.6 Translation Operators inThreeDimensions...................................186 3.15 Functions inRotated Coordinates................................................................186 3.15.1 Rotating Functions..........................................................................186 3.15.2 Rotation Operator............................................................................188 3.15.3 Rectangular Coordinates for theGenerator of Rotations about z.........................................................................189 Contents vii 3.15.4 Rotation ofthe Position Operator...................................................189 3.15.5 StructureConstants and LieGroups...............................................190 3.15.6 StructureConstants forthe Rotation Lie Group.............................191 3.16 DyadicNotation............................................................................................192 3.16.1 Notation...........................................................................................192 3.16.2 Equivalence between the Dyad and theMatrix..............................192 3.17 Review Exercises..........................................................................................193 References and Further Reading.............................................................................199 Chapter 4 Fundamentals of Classical Mechanics....................................................................201 4.1 Constraints and Generalized Coordinates.....................................................201 4.1.1 Constraints.......................................................................................201 4.1.2 Generalized Coordinates..................................................................202 4.1.3 PhaseSpace Coordinates.................................................................204 4.2 Action,Lagrangian, and Lagrange’sEquation.............................................204 4.2.1 Origin ofthe Lagrangian inNewton’sEquations...........................205 4.2.2 Lagrange’s Equation from a Variational Principle..........................207 4.3 Hamiltonian..................................................................................................210 4.3.1 Hamiltonian from the Lagrangian...................................................210 4.3.2 Hamilton’s Canonical Equations.....................................................211 4.4 Poisson Brackets...........................................................................................213 4.4.1 Definition of thePoissonBracket and Relation to theCommutator...........................................................................213 4.4.2 BasicProperties forthe PoissonBracket........................................214 4.4.3 Constants ofthe Motion and Conserved Quantities.......................215 4.5 Lagrangian and Normal Coordinates fora Discrete Array ofParticles.......216 4.5.1 Lagrangian and Equationsof Motion..............................................216 4.5.2 Transformationto Normal Coordinates..........................................217 4.5.3 Lagrangian and theNormal Modes.................................................222 4.6 ClassicalField Theory..................................................................................224 4.6.1 Lagrangian and Hamiltonian Density.............................................225 4.6.2 Lagrange Density for1-D WaveMotion........................................227 4.7 Lagrangian and theSchrödinger Equation...................................................230 4.7.1 Schrödinger Wave Equation............................................................230 4.7.2 Hamiltonian Density........................................................................231 4.8 Brief Summaryof theStructureof Space-Time...........................................232 4.8.1 Introduction toSpace-Time Warping..............................................232 4.8.2 Minkowski Space............................................................................233 4.8.3 Lorentz Transformation...................................................................236 4.8.4 SomeExamples...............................................................................238 4.9 Review Exercises..........................................................................................239 References and Further Readings............................................................................243 Chapter 5 Quantum Mechanics................................................................................................245 5.1 Relation between Quantum Mechanics and Linear Algebra.......................................................................................245 5.1.1 Observables and Hermitian Operators............................................246 5.1.2 Eigenstates.......................................................................................247 5.1.3 Meaning ofSuperpositionof Basis States and the Probability Interpretation....................................................249 viii Contents 5.1.4 Probability Interpretation.................................................................250 5.1.5 Averages..........................................................................................252 5.1.6 Motionof theWaveFunction.........................................................254 5.1.7 Collapse ofthe Wave Function.......................................................255 5.1.8 Interpretationsof theCollapse........................................................257 5.1.9 Noncommuting Operatorsand the Heisenberg Uncertainty Relation........................................................................259 5.1.10 Complete Sets of Observables.........................................................262 5.2 Fundamental Operatorsand Procedures forQuantum Mechanics...............263 5.2.1 Summary ofElementary Facts........................................................263 5.2.2 Momentum Operator.......................................................................264 5.2.3 Hamiltonian Operator and theSchrödinger Wave Equation................................................................................264 5.2.4 Introduction toCommutation Relationsand Heisenberg Uncertainty Relations......................................................................266 5.2.5 Derivation ofthe Heisenberg Uncertainty Relation........................267 5.2.6 Program...........................................................................................269 5.3 Examples forSchrödinger’sWaveEquation................................................271 5.3.1 Discussion ofQuantum Wells.........................................................272 5.3.2 Solutions to Schrödinger’s Equationfor theInfinitely Deep Well........................................................................................273 5.3.3 FinitelyDeep SquareWell..............................................................279 5.4 Harmonic Oscillator......................................................................................285 5.4.1 Introduction toClassical and Quantum Harmonic Oscillators.......................................................................285 5.4.2 Hamiltonian for theQuantum Harmonic Oscillator........................288 5.4.3 Introduction tothe Ladder Operators for theHarmonic Oscillator.............................................................288 5.4.4 LadderOperators inthe Hamiltonian..............................................290 5.4.5 Properties of theRaising and Lowering Operators.........................292 5.4.6 EnergyEigenvalues.........................................................................294 5.4.7 EnergyEigenfunctions....................................................................294 5.5 Introduction to Angular Momentum............................................................296 5.5.1 ClassicalDefinition ofAngular Momentum...................................296 5.5.2 Origin ofAngular Momentum in Quantum Mechanics..................297 5.5.3 Angular Momentum Operators.......................................................298 5.5.4 Picturesfor Angular Momentum inQuantum Mechanics..............299 5.5.5 Rotational Symmetry and Conservation of Angular Momentum....................................................................301 5.5.6 Eigenvalues and Eigenvectors.........................................................303 5.5.7 Eigenvectors asSpherical Harmonics.............................................305 5.6 Introduction to Spinand Spinors..................................................................309 5.6.1 BasicIdea ofSpin...........................................................................309 5.6.2 Link between PhysicalSpace andHilbert Space............................312 5.6.3 Pauli SpinMatrices.........................................................................315 5.6.4 Rotations..........................................................................................317 5.6.5 Direct Product Spacefor a Single Electron....................................318 5.6.6 SpinHamiltonian.............................................................................319 5.7 Angular Momentum for Multiple Systems..................................................323 5.7.1 AddingAngular Momentum...........................................................323 5.7.2 Clebsch–Gordon Coefficients..........................................................326 Contents ix 5.8 Quantum Mechanical Representations.........................................................330 5.8.1 Discussion ofthe Schrödinger,Heisenberg, and Interaction Representations......................................................331 5.8.2 Schrödinger Representation.............................................................333 5.8.3 Rate of Change of theAverageof an Operator in theSchrödinger Picture...............................................................334 5.8.4 Ehrenfest’sTheorem for theSchrödinger Representation..............335 5.8.5 Heisenberg Representation..............................................................337 5.8.6 Heisenberg Equation.......................................................................338 5.8.7 Newton’sSecondLaw from the Heisenberg Representation..........339 5.8.8 Interaction Representation...............................................................340 5.9 Time-Independent PerturbationTheory........................................................341 5.9.1 Initial Discussionof Perturbations..................................................341 5.9.2 NondegeneratePerturbationTheory................................................342 5.9.3 Unitary Operator forTime-Independent Perturbation Theory.........................................................................349 5.10 Time-Dependent Perturbation Theory..........................................................352 5.10.1 Physical Concept.............................................................................353 5.10.2 Time-Dependent Perturbation Theory Formalism in theSchrödinger Picture...............................................................355 5.10.3 Example forFurther Thought and Questions..................................359 5.10.4 Time-Dependent Perturbation Theory in theInteraction Representation.................................................................................362 5.10.5 Evolution Operator in theInteraction Representation.................................................................................364 5.11 Introduction to Optical Transitions..............................................................365 5.11.1 EM Interaction Potential..................................................................365 5.11.2 Integral for theProbability Amplitude............................................367 5.11.3 Rotating WaveApproximation.......................................................369 5.11.4 Absorption.......................................................................................370 5.11.5 Emission..........................................................................................371 5.11.6 Discussion ofthe Results................................................................372 5.12 Fermi’sGolden Rule.....................................................................................373 5.12.1 IntroductoryConcepts on Probability.............................................373 5.12.2 Definition of theDensity ofStates..................................................374 5.12.3 Equations forFermi’s Golden Rule................................................377 5.13 Density Operator...........................................................................................382 5.13.1 Introduction tothe DensityOperator..............................................382 5.13.2 Density Operator andthe Basis Expansion.....................................386 5.13.3 Ensemble and Quantum Mechanical Averages...............................390 5.13.4 Lossof Coherence...........................................................................394 5.13.5 SomeProperties...............................................................................396 5.14 Introduction to Multiparticle Systems..........................................................397 5.14.1 Introduction.....................................................................................397 5.14.2 Permutation Operator......................................................................399 5.14.3 Simultaneous Eigenvectorsof theHamiltonian and the Interchange Operator..........................................................401 5.14.4 Introduction toFockStates.............................................................403 5.14.5 Origin ofFockStates......................................................................404 5.14.5.1 Bosons..............................................................................406 5.14.5.2 Fermions..........................................................................408
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