Physics of Surfaces
Objectives
The aim of the course is to illustrate the morphologic, electronic ad optical properties developed by surfaces and interfaces of crystalline solids. Surfaces and interfaces represent examples of lowdimensional systems, where the symmetry reduction may induce novel and exotic properties with respect to those that can be observed inside the bulk of a solid. The physical mechanisms acting inside the bulk or at the surface of a solid will be compared in order to highlight their role in defining how the electronic and optical properties of solid matter are influenced by symmetry reduction. During the course the students will be also introduced to a few experimental techniques that are currently employed in modern Surface Science.
Syllabus
Band structure.
Examples of simple metals, 3d metals and insulators. Nearly free electron model and tight binding approximation.
Density of states: examples in 1, 2 and 3 dimensions.
Surface electronic states: projected bands structure, Shockley states, Tamm states.
Beyond the single particle approximation: Anderson and Hubbard models.
Selected examples: graphene, topological insulators, …
Optical properties.
KramersKronig relations. Direct and indirect transitions. Joint density of states in 1, 2 and 3 dimensions.
Excitons and plasmons. Surface plasmons and plasmonics.
Experimental techniques.
Surface preparations and thin film growth.
Structural characterization of surfaces: LEED.
Electronic structure determination: photoemission (UPS, XPS, ARPES), Auger spectroscopy, microscopy
BIBLIOGRAPHY:
AshcroftMermin “Solid State Physics”, Luth “Solid surfaces, Interfaces and Thin Films”, (Hofmann “Solid state physics”, M. Fox “Optical properties of solids”)
Thin films: Magnetism and Superconductivity
Objectives
The course presents two important phenomena that are strongly influenced by dimensionality: magnetic order and superconductivity. Both subjects are presented at a general level in solids and discussed for their modifications in thin films, at interfaces and in solids characterized by an intrinsic reduced dimensional (2D or 1D) structure. Some experimental technique for the exploration of relevant magnetic and electronic properties are also described. The aim is to broaden the knowledge of important ordering phenomena in solids and to underline how dimensionality may alter them.
Syllabus
Magnetism of isolated magnetic moments
Phenomenology: recalling diamagnetism, paramagnetism and atomic moments.
Crystal field: origin of CF, quenching of orbital moments, JahnTeller effect.
Exchange interaction.
Magnetic order and magnetic structures.
Heisenberg and Ising models.
Magnetism in metals
Pauli paramagnetism, Landau diamagnetism, Stoner model, RKKY interaction.
Excitations in magnetic systems.
Spin waves, Stoner excitations
Magnetism at low dimensionality.
Spin chains and spin ladders, 2 dimensional magnets, thin films.
Superconductivity: phenomenology, London equations, Josephson effect, BCS theory, Cuprate superconductors (also as an example of 2D antiferromagnets).
Experimental techniques.
Magnetic resonances, Mössbauer spectroscopy.
Elastic and inelastic scattering for magnetic structure and magnetic excitations.
Magnetooptical techniques.
Bibliography
S. Blundell “Magnetismm in condensed matter”, Oxford University Press
AshcroftMermin “Solid State Physics”, Saunders College.
Prerequisites
Bachelor courses on Quantum physics, Structure of matter and Mathematics. Master course in Solid state physics.
