凝聚态物理导论-中科院课件-苏刚chapter1

Chapter 1 Introduction §1.1 Preamble Physics is the science that studies the structures of matter and the fundamental laws of motion of matter. Classical mechanics17th century: Newton’s mechanics, gravitation 18th -19th century: Atomic theory (Dalton); Electromagnetic field theory (Faraday, Maxwell); Coulomb law Classical theory of electromagnetism 19th century: about 60 elements uncovered, Mendeleev’s periodic table of elements; discoveries of electrons, αparticle, radiation, x-ray, etc. Early of 20th century: conflict between atomic structure model and classical physics Quantum mechanics; Relativity Since mid of 20th century: advances of physics lead to sub-branches: atomic and molecular physics, condensed matter physics, nuclear physics, elementary particles and fields, plasma, optics, …… 4 fundamental forces exist in Nature: Force Strength Strong (Yukawa) 1 Electromagnetic 10-2 Weak (βray) 10-13 Gravitation 10-38 Grand unification of these 4 forces is unsuccessful up to date. States of matter: Gas, liquid, solid, plasma, Bose-Einstein condensation Standard model of Universe: Quarks incorporated to form hadrons 10-44s Separation of gravitation from other forces 10-36s Separation of weak and strong interactions 10-10s 10-6s 1012s Separation of weak and electromagnetic forces Atoms appear Big bang present Energy and length scales: quark >100 GeV GeV MeV eV meV proton nuclear atom, molecule, cluster solid Ultra high energy physics High energy physics Medium low energy physics Condensed matter physics <10-17 m 10-15 m a few times 10-15 m 10 -10 m 10-9 ~10-6m 100 m The smaller the particle, the higher the energy. The development of condensed matter physics also pushes forward the advances of other sub-fields of physics, e.g. particle physics, astronomy, etc. The concepts, such as phase transitions, symmetry breaking, topological defects, infra-red divergence, etc., come first from condensed matter physics. The development of condensed matter physics also plays an important role in the discoveries of modern technologies that alter dramatically our daily life. For instance, transistor, laser, liquid crystal display, integrated circuit, optical fiber, etc. §1.2 Development of solid state physics 1. Crystallography ¾ The theory of symmetry in crystals has been established at the end of 19th century. ¾ Laue (1912): discovered x-ray diffraction phenomenon in crystals, indicating the periodic structure of crystals. ¾ Braggs’ (1913-14): x-ray-based analytic method on measuring crystal periodic structures. ¾ Ewald (1916-1917): propagation of electromagnetic waves in periodic structures of crystals, leading to the x-ray dynamic diffraction theory. 2. Theory of specific heat in solids ¾ Einstein (1906, 1911): quantum theory based on independent oscillators, qualitatively consistent with experiments, but inconsistent at low temperatures. ¾ Debye (1912): famous T3 law, which is based on the coupled oscillators, leading to the independent oscillators with different frequencies. ¾ Born & von Karman (1940-50): elastic waves in periodic structures, establishing the foundation of lattice dynamics. 3. Free electron theory in metals ¾ Drude, Lorentz (1900, 1905): classic theory based on free electrons, which cannot explain why the metallic conductivity is so high but the contribution of electrons to the capacity is so small. ¾ Pauli, Sommerfeld (1928): Free electron theory based on Fermi- Dirac statistics, which can explain some features of metals, but is still inadequate to explain the conducting properties in metals. 4. Ferromagnetism ¾ Magnetism was discovered in ancient times, for instance, compass for sailing. At the end of 19th century, a little is known for ferromagnetism experimentally. ¾ Curie (1895): Curie’s law, magnetic susceptibility is inversely proportional to temperature for paramagnets. ¾Weiss (1907): molecular-field theory---mean-field theory for ferromagnetism. ¾ Heisenberg (1926): Quantum theory of magnetism based on quantum mechanics. Subsequent milestone experiments and theories result in the occurrence of two sub-fields of solid state physics: Band theory; Lattice dynamics ‡ Bethe (1928): propagation of de Broglie waves in periodic structures---dynamic theory of electron diffraction; ‡ Bloch (1928): band theory for metallic conduction; ‡Wilson (1931): band theory for metals and insulators, foundation of semiconductor physics; ‡ Born (1940s): lattice dynamics; ‡ Brillouin (1946): band theory and lattice dynamics---consequences of propagation of waves in periodic structures: lattice dynamics (propagation of elastic waves), band theory (propagation of de Broglie waves or electrons in crystal lattice); ‡ end of 1940s: development of semiconductor physics, invention of transistors; ‡ 1947: APS coined the name “solid state physics”; ‡ 1950s: theories of superconductivity and superfluidity; ‡ 1960s: periodic structures → aperiodic structures; localized states in disordered systems; theory of noncrystalline solids. Solid state physics: crystal structure, reciprocal lattice, lattice dynamics, band theory, semiconductor, superconductivity, magnetism, amorphous solids, etc. §1.3 Emergence of condensed matter physics Since 1970s, the topics studied in solid state physics have been extended: Periodic structures with translational invariance Aperiodic structures, artificial structures, incommensurate structures 3-dimensional (3D) crystals Reduced dimensional (1D, 2D, 0D, fractional dimensional) crystals; quasicrystals, superlattices Ordered systems Disordered systems; quantum coherence solids Soft matter (liquid, polymers, granular…) Macro-, microscopic Mesoscopic, clusters Theoretical methods in solid state physics have been enriched: Quantum mechanics + statistical physics Computer simulations (e.g. First-principles, molecular dynamics, Monte Carlo, …. ) Electromagnetic properties in solid states Liquid-like properties (Fermi liquid, Bose liquid, Luttinger liquid, etc.) Properties of different condensed systems Revealing the same physics (e.g. scaling law, universality, etc.) Some physical phenomena in solids Can be found in other condensed systems Consequently 9 Topics under investigation become extended and complex; 9 Basic concepts and theoretical methods are highy enriched; 9 The connections between metallic physics, semiconductor physics, magnetics, low-temperatrue physics, dielectric physics, statistical physics, etc., become closer; 9 New sub-fields such as disordered systems, quasicrystals, mesoscopic physics, cluster physics, and so on, are established; 9 Some common physics in condensed phases, like symmetry breaking, critical phenomenon, universality of scaling, elementary excitations, etc., are acknowledged; 9 1963: Busch edited a journal entitled “Physics of condensed matter”. 9 1978: APS voted to change “solid state physics” to “condensed matter physics”. Condensed matter physics is the science that studies microscopically the structures, laws of motion, and macroscopic properties of condensed mater composed of interacting many particles. Important concepts in condensed matter physics: order parameter, symmetry breaking, elementary excitations, generalized rigidity, defects, scaling law, universality, self-similarity, etc. Simplicity vs. Complexity In physics: complexity (many-particle systems) → simplicity (single-particle systems, simple systems) In Nature: simplicity (fundamental laws) → complexity of Nature (e.g. life phenomena) Emergent phenomena §1.4 Topics in condensed matter physics The topics in condensed matter physics are enormous. Generally speaking, they are focused on two aspects: (I) Structure, mechanical, thermal and acoustical properties in condensed matter; (I) Electronic structure, electrical, magnetic and optical properties in condensed matter. ¾ Structure of solids and liquids; crystallography ¾Mechanical and acoustical properties of condensed matter ¾ Lattice dynamics ¾ Equations of state, phase equilibria, and phase transitions ¾ Thermal properties of condensed matter ¾ Nonelectronic transport properties of condensed matter ¾ Quantum fluids and solids ¾ Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties) (I) Structure, mechanical, thermal and acoustical properties in condensed matter ¾ Electronic structure of bulk materials ¾ Electronic transport in condensed matter ¾ Electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures ¾ Superconductivity ¾Magnetic properties and materials ¾Magnetic resonances and relaxations in condensed matter, Mössbauer effect ¾ Dielectrics, piezoelectrics, and ferroelectrics and their properties ¾ Optical properties, condensed-matter spectroscopy and other interactions of radiation and particles with condensed matter ¾ Electron and ion emission by liquids and solids; impact phenomena (II) Electronic structure, electrical, magnetic and optical properties in condensed matter 1. The quantum mechanics of large, interacting systems; 2. The structure and properties of materials at reduced dimensionality; 3. Materials with increasing complexity in composition, structure, and function; 4. Nonequilibrium processes and the relationship between molecular and mesoscopic properties; 5. Soft condensed matter and the physics of large molecules, including biological structures; 6. Controlling electrons and photons in solids on the atomic scale; 7. Understanding magnetism and superconductivity; 8. Properties of materials under extreme conditions; 9. Materials synthesis, processing, and nanofabrication; 10. Moving from empiricism toward predictability in the simulation of materials properties and processes. Strategic Scientific Themes in Condensed Matter and Materials Physics