Physics Conf. Dr. Radu Fechete Technical University of Cluj-Napoca

Content 1 Davisson-Germer experiment Davisson-Germer experiment Barrier of potential. Tunnel effect Barrier of potential. Tunnel effect The Hydrogen atom The Hydrogen atom Quantum numbers Quantum numbers Stern and Gerlach experiment Stern and Gerlach experiment Atomic orbitals Atomic orbitals Atomic spectra Atomic spectra Holography Holography

Davisson-Germer experiment

Barrier of potential. Tunnel effect

The Hydrogen atom Laguerre polynomial Legendre polynomial Quantified energy

Quantum numbers n – principal quantum numbers l – orbital quantum number m – magnetic quantum number Bohr magneton

Stern and Gerlach experiment Energy of a magnetic moment in B Spin quantum number

Atomic orbitals

Atomic spectra

-wave number The theory of quantum transitions Rydberg consntant H =  10 7 m -1 = 2.15  J = 13.6 eV

LASERs Def: light amplification by stimulated emission of radiation Probability of spontaneous emission Probability of spontaneous absorption Boltzmann distribution Probability of stimulated emission

Holography

Content 2 Semiconductors Semiconductors Hall Effect Hall Effect Difference of potential at metal-metal contact Difference of potential at metal-metal contact Thermoelectric effect (Seebeak effect) Thermoelectric effect (Seebeak effect) Magnetic materials Magnetic materials Diamagnetism Diamagnetism Paramagnetism Paramagnetism Ferromagnetism Ferromagnetism Superconductivity Superconductivity

Energetic Bands in solids

Semiconductors:

Hall Effect

Difference of potential at metal- metal contact

Thermoelectrically effect (Seebeck effect) The Peltier effect is considered the inverse of thermoelectric effect consisting in the heat radiation while an electrical current passes through an electical circuit consisting from two different materials: Thermoelectrically effect consist in the apparition of an electromotive tension into a two-metals electrical circuit when a difference of temperature exist between those two contact points.

Magnetic properties of materials The total magnetic moment Sample magnetization

Magnetic properties of materials H – magnetic field intensity  m – magnetic susceptibility  r – material relative magnetic permeability  – material magnetic permeability

Substances classification Diamagnetic: (  m < 0 – small;  m   m (T)) Diamagnetic: (  m < 0 – small;  m   m (T)) Paramagnetic (  m > 0) Paramagnetic (  m > 0) Paramagnetic: (  m > 0 – small; - Curie law) Paramagnetic: (  m > 0 – small; - Curie law) Ferromagnetic (  m > 0 – large;  m =  m (T)) Ferromagnetic (  m > 0 – large;  m =  m (T)) Antiferromagnetic Antiferromagnetic Ferrimagnetic. Ferrimagnetic.

Magnetic materials: Diamagnetism The materials with no permanent magnetic moments are diamagnetic materials. The diamagnetism originates in the change of the electrons orbit in the presence of the external magnetic field.

Paramagnetic materials Curie law

Ferromagnetic materials Ferromagnetic materials are characterized by magnetic memory: Hysteresis curves. H c – coercitive fields B s – saturation field B r – remanent magnetization

Ferromagnetic materials Due to the reorientation of elementary magnetic moments the sample magnetization increases with the increase of the external magnetic field. Barkhausen effect – the increase of magnetization appears in steps. Curie-Weiss law

Magnetic materials Paramagnetic Ferromagnetic Antiferromagnetic Ferrimagnetic Forced ferromagnetic

Superconductivity An element (inter-metallic alloy, ceramics etc.) that will conduct electricity below a certain temperature without resistance.

Superconductor material: Typical structure

Superconductivity : Meissner effect

The origin of superconductivity Cooper pairs John Bardeen, Leon Cooper si Robert Schrieffer (BCS theory), after 60 years from the discovery of the supra-conductibility phenomena, assumes that the Cooper pairs are now bosons and are no longer subjected to the Pauli principle of exclusion. The electrons motion inside of superconductor material is perfectly ordered and the interaction with the network is much reduced.

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