Examiner: 2255 Professor Tord Claeson
AIM OF SUBJECT
The area of low temerature physics is vast. Within most parts of condensed matter physics one makes use of low temperatures. The course will treat
1) low temperature technology, i.e. an overview of cooling methods, thermal properties of
materials, measurement of temperatures, etc.
2) properties of liquid helium, i.e. macroscopic quantum liquids.
3) studies of superconductors (about 50% of the course), both microscopic and macroscopic
properties, including Josephson effects.
CONTENT
Cooling methods, cryostat construction and temperature measurement. Properties of He4, superfluidity. He3 as a Fermi liquid. Phenomenological models of superconductivity. Type I and type II superconductors. Ginzburg-Landau theory. Microscopic models (Bardeen-Cooper-Schrieffer - BCS) for superconductivity. Tunneling in superconductors. Macroscopic quantum effects.Technical applications. High-temperature superconductors. Practical laboratory work.
The course may be regarded as a practical application of quantum physics, statistical physics, condensed matter physics and thermodynamics. Liquid He3 and He4 are the only known examples Fermi and Bose liquids. Spectacular properties of these liquids (e.g. motion without friction) can be related to the particular properties of these statistical distributions.
To discuss different cooling principles one must apply thermodynamic laws. New advanced cooling methods leads to temperatures of the order of 10-5 K.
To understand the nature of superconductivity we must apply knowledge of condensed matter physics. Certain properties of a superconductor can actually be calculated with an order -of-magnitude better accuracy then in the non-superconducting state. The recent discovery of high-temperature superconductors, e.g. HgBaCaCuO with Tc in the 135-160 K range, represents a break-through with great possibilities for important applications in electronics and power transport. The high-Tc research is highly cross-disciplinary. Many aspects are still unclear in spite of intense research. The course will discuss properties and models for high-Tc superconductors.
Quantum mechanics can be applied on a macroscopic scale in superconductores. Interference between electrons moving through parallell Josephson junctions gives rise to vector-potential dependent supercurrents. This may be utilized in hypersensitive instruments and detectors (SQUID; used in detecting and imaging the brain activity via magnetic fields). The course will also discuss aspects of Mesoscopic Physics, on the border between atomic and macroscopic structures (e.g. nansosystems).
LITERATURE
Lecture notes.
Reference books.