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EPSRC Reference: EP/C009487/1
Title: A cryogen-free single-millikelvin system for measurement on nanoelectronic devices and quantum spin systems
Principal Investigator: Lonzarich, Professor GG
Other Investigators:
Smith, Professor CG Ford, Professor CJB
Researcher Co-Investigators:
Project Partners:
Cambridge Magnetic Refrigeration Ltd
Department: Physics
Organisation: University of Cambridge
Scheme: Standard Research (Pre-FEC)
Starts: 01 July 2005 Ends: 30 June 2009 Value (£): 731,016
EPSRC Research Topic Classifications:
Condensed Matter Physics Instrumentation Eng. & Dev.
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:  
Summary on Grant Application Form
The aim of this research is to build an instrument that can very quickly and cheaply take metallic and semiconducting samples to temperatures of 1 mK above absolute zero. The samples to be studied are (i) semiconducting devices which have been designed like laboratories on a chip to investigate quantum transport phenomena and (ii) ultra-pure conducting materials on the border of phase transitions near absolute zero of temperature in which novel quantum behaviour is expected to arise. At the moment, it takes about a week to take a sample to 50 mK above absolute zero. 1 mK is a factor of 50 times colder and at these temperatures the number of unwanted fluctuations which can disturb complex quantum states is greatly reduced. Pure quantum states defuse out to cover an increasing volume with time, but eventually an unwanted scattering event disturbs the state destroying more complex interactions between the states. These interactions are what we would like to investigate. There are many groups in the world working to try and use quantum devices to construct a quantum computer that could handle more variable than there are atoms in the universe. This instrument will greatly help in achieving that goal because it will have a scanning probe which is capable of constructing sub-micron electronic devices at these extremely low temperatures. The scanning probe can also image the devices and image the coherent quantum electron states in these devices.To take a sample down to these temperatures usually involves complex cryostats containing liquefied gases which are very expensive to produce and time consuming to handle. This cryostat has no liquid gases, but is instead cooled by an ultra-low noise cryocooler combined with a technique for cooling involving aligning spins in a magnetic field so that they are ordered, a bit like the atoms in a solid are ordered. The small amount of heat in the probe we wish to cool then melts this ordered lattice (the coolant) which reduces the probe temperature. This is a similar process to using ice cubes (the coolant) to keep a drink (the probe) cold. Because we are not using very expensive liquefied gases, and because of the low level of maintenance and training that would be required, the direct and indirect costs of running the proposed system can be more than 10 times lower than the cost of running a conventional system that would only reach a temperature 50 times higher.The research being carried out is extremely complex and requires very careful sample preparation and measurement setups. These experiments often need to be modified or altered slightly to get the best results. With existing instruments it can take over two weeks to change sample or modify a sample set up. With the new low temperature scanning probe instrument, we can change the sample configuration in hours and with this new cryogen-free set up we can change the experiment in a day. This is a substantial improvement in throughput with a substantial reduction in running costs. The total capital outlay for the instrument is also lower than for comparable systems that would only reach an order of magnitude higher temperatures.
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Organisation Website: http://www.cam.ac.uk