LOW TEMPERATURE PHYSICS


Studies of materials at the lowest attainable temperatures provide key insights into the underlying physics of modern materials whose applications often lead to new technological breakthroughs. Our Department offers a broad range of research opportunities in this area, with one of the best equipped, largest groups in the world. In addition to eight individual laboratories with dilution refrigerator capabilities, the facilities include the specially designed Microkelvin Laboratory that has three nuclear demagnetization refrigerators; two with copper nuclear refrigerators for Tmin below 100 ľK, and one with a PrNi5 demagnetization stage for high cooling power down to 300 ľK. The latter is a dedicated High B/T facility for the National High Magnetic Field Laboratory and is open to qualified external users as well as local groups who need to study materials at high magnetic fields (up to 16.5 T) and low temperatures (down to 300 ľK) simultaneously. The High B/T facility is operated by Dr. Jian-Sheng Xia, and Dr Naoto Masuhara assists with the scientific and technical programs of the Microkelvin Laboratory.

In addition to the permanent research scientists and engineers, the research efforts include graduate and undergraduate students, postdoctoral scholars, and distinguished visitors. Current research activities include:

Quantum Solids: Programs underway study the diffusion of impurities in the so-called supersolid phase of 4He, and the behavior of the quantum solids 3He and HD in monolayer films and nanostructured geometries. In addition, researchers are exploring the behavior of adsorbed molecules in zeolite-like nanoporous materials for applications to hydrogen storage and catalysis.

Quantum Fluids: A variety of quantum phenomena are explored in different liquids, including normal fluid and superfluid states of 3He in restricted geometries and cryogenic helium turbulence in 4He. The generation of the highest Reynolds numbers possible in the laboratory is an active area of research.

Quantum Spins: Emerging aspects of the quantum mechanical interactions of spins and electrons in novel arrangements found in molecule-based magnetic systems and heterostructured thin films are investigated. The materials typically possess a restricted geometry, as a one-dimensional chain or a two-dimensional film, where new phenomena and states of matter exist. The extremes of temperature and magnetic field allow the ground states of these systems to be studied and provide fundamental tests of theoretical models.

Collaborative Research Efforts include experimental particle astrophysics and biophysics. Current astrophysics projects are using novel very low temperature techniques to detect the subatomic particles that constitute the cosmological dark matter, including (i) large scale subterranean experiments for the detection of WIMPS, and (ii) ultra-low noise microwave detectors in the search for axions. Collaborative biophysics projects are studying the influence of strong magnetic fields on gene expression.

The development of new techniques and thermometry standards is also a significant part of the research program. For example, low temperature sensor development, with special attention to capacitive pressure, transducers and their applications to ultra-low temperature thermometry using the melting pressure of 3He, is being pioneered. Experimental capabilities include ultra-sound and NMR spectroscopies, high sensitivity magnetic susceptibility and heat capacity measurements.