1. PROGRESS REPORT.......................................................................................................
1.1. Summary of the activities and major achievements ................................................................
1.2. Management overview ...........................................................................................
1.3. Description of the publicity concerning the new opportunities for access.....
1.4. Description of the selection procedure ................................................................
1.5. Transnational Access activity ................................................................................
1.6. Scientific output of the users at the facility ...........................................................
1.7. User meetings ..........................................................................................................
1.8. Update of the non-confidential Project information............................................
Annex 1 - Composition of the Users Selection Panel
Annex 2 - List of User-Projects
Annex 3 - List of Users
Annex 4 - List of publications
Annex 5 - Updated non-confidential Project information
1.1. Summary of the activities and major achievements
The ULTI infrastructure access program is funded by European Commission for the four-year period from 1.4.2004 to 31.3.2008. During the second year of operation the Selection Panel conducted four email meetings and accepted 23 new projects into the program. ULTI program supported altogether 14 users in 14 different projects. Six of the projects were new, and the remaining eight extensions of the projects started during the first year of operation. Five of the active projects were completed during the reporting period.
The 14 users came from eight different countries, seven from Europe and one from Israel. Five of the users were new, first time users. Finally, first time in the history of ULTI, we had a female user.
The 14 supported projects cover a variety of topics from vortex physics and turbulence in superfluids, to quantum crystals, and to quantum electronics in mesoscopic normal metal and superconducting structures. Nine of the projects were experimental and five theory projects.
During the reporting period ULTI-results were published in 10 high-level scientific articles. Eight additional articles were submitted and are waiting for acceptance. One of the articles appeared in highly respected Reviews of Modern Physics  with impact factor over 30, three in Physical Review Letters (IF > 7), and one in Applied Physics Letters (IF > 4). One should also notice that the previous ULTI program produced another article in Reviews of Modern Physics [ULTI III: 1], which appeared during this reporting period.
One of the hottest topics in mesoscopic electron physics is the superconductivity in carbon nanotubes. Three years ago a European research group has reported the observation of intrinsic superconductivity in a bundle of single walled carbon nanotubes (SWNT). Later, two other European groups observed proximity-effect-induced superconductivity in individual SWNTs. Finally, in ULTI project #2, proximity-effect-induced superconductivity was observed in gate-controlled individual multiwalled carbon nanotubes, in contact with superconducting titanium-leads. This will strengthen European leadership in the investigation of superconductivity in one-dimensional carbon nanotubes.
1.2. Management overview
No significant management tasks were carried out during the second year of the ULTI program. The program continues to offer the visitors professional scientific, technical and logistic support. The program secretary Ms. Satu Pakarinen left her position at the Low Temperature Laboratory on March 14, 2006, and was replaced by Mrs. Leena Meilahti.
We are continuously upgrading the WEB-page of the ULTI program (http://boojum.hut.fi/eu.html), to provide information about the status of the accepted projects and effective communication channel between the Selection Panel, visitors and the ULTI facility.
During the present reporting period the ULTI program finally had its first female user in project #19.
1.3. Description of the publicity concerning the new opportunities for access
The ULTI program was presented to the European low temperature physics community in the recent ULTI user meeting organized in Lammi, Finland in April 21- 26, 2006. The Lammi meeting was widely advertised within the community and old and potential new users were invited to participate. Altogether 101 scientists from 22 countries, among them 7 members of the Selection Panel, participated and many of them paid a site visit to the Low Temperature Laboratory.
1.4. Description of the selection procedure
The selection of users was conducted by email vote in 27.5.2005, 18.11.2005, 18.1.2006 and 16.3.2006. A list of candidates, based on the received proposals, was prepared for the vote by the ULTI manager.
One proposal was rejected because the suggested experiment could not be conducted in the facility.
1.5. Transnational Access activity
The complete list of User-Projects and Users can be found in Annexes 2 and 3, respectively (MS Access, Annex 2 and 3).
During its first year of operation, 18 projects were accepted to the ULTI program by the Selection Panel. During the second program year 23 new projects, 12 experimental and 11 theoretical ones, were added. However, only 14 projects were active during the present reporting period. Within the active projects 14 scientists from 8 different countries were supported by ULTI. Five of the scientists were new users and one a female user.
The visitors spent altogether 18.17 person months at the ULTI facility. Compared to the first year of operation (18 visitors, 16 projects, and 15.10 person months) the ULTI program has continued in a steady operational mode without difficulties. Two of the projects (#1 and 8) were completed during the first year and five more (# 2, 7, 12, 16 and 17) during the second year of operation.
The supported projects cover a variety of topics from vortex physics and turbulence in superfluids (#7, 11, 13, 15, 16, and 17), to quantum crystals (#18), and to quantum electronics in mesoscopic normal metal and superconducting structures (#2, 5, 9, 19, 23, 24, and 26). Nine of the projects were experimental (#2, 5, 7, 13, 15, 16, 17, 18, and 19) and five theory projects (# 9, 11, 23, 24, and 26). The experimental projects were allocated 13.35 (73.5%) and the theory projects 4.83 person months (26.5%).
1.6. Scientific output of the users at the facility
In addition to the major achievement in the studies of superconductivity in multiwalled carbon nanotubes, reported in 1.1., the following interesting results have been obtained during the second year of ULTI program:
Spin Current Turbulence (project # 11)
In this project, Prof. Bunkov has been working on a theoretical analysis on the sudden appearance of excessive relaxation losses in a critical temperature regime of an important resonance mode of 3He-B, the so-called Homogenously Precessing Domain (HPD). The HPD mode is currently the most important example of a dynamic coherent order parameter state, where the entire spin magnetization precesses with the drive from the externally applied radio frequency excitation field. The large relaxation in the critical temperature regime, nearly 20-year-old mystery, is now explained to arise from a mode crossing where the excitation pumping escapes into two new modes. A report on this explanation is under preparation together with two theorists with whom he worked on this problem during his stay at the ULTI facility .
Experiments of Mesoscopic SQUID Arrays (project #19)
The goal of this project was to learn about high frequency properties of Josephson junction and SQUID arrays and to make use of them in experiments on Cooper pair pumps and as switches.
Experiments on Cooper pair pumps with SQUID arrays have proven to be difficult due to the arbitrary background charges affecting the small islands between the SQUIDs. However, an experiment where SQUIDs were used as switches of photonic heat transport between tiny normal metal islands has worked out beautifully, and the first observation ever of this heat transport mechanism has been recorded. At higher temperatures, heat is mainly transported by phonons. The photonic heat transport becomes important at lower temperatures below 100 mK. It may eventually help to cool mesoscopic electron samples into the sub-mK regime, which has so far been a difficult task. Also, a simple model explaining the observations quantitatively has been developed. This work will be submitted for publication in Nature.
Other highlights of the important results among the user-projects/see Annex 4
1.7. User meetings
No user meetings were organized during the second reporting period. However in April 2006, immediately at the beginning of the third reporting period, the first ULTI user meeting was held in Lammi, Finland for 101 participants.
1.8. Update of the non-confidential Project Information
See Annex 5
1. Balibar, S., Alles, H., and Parshin, A., The surface of helium crystals, Reviews of Modern Physics, 77, p. 317-370 (2005).
Project # 3:
1. Kivotides, D., Turbulence without inertia in thermally excited superfluids, Physics Letters A, 341, p. 193-197 (2005).
Project # 5:
2. Pekola J.P., Heikkila T.T. Savin A.M., Flyktman J.T., Giazotto F., and Hekking F.W.J., Limitations in cooling electrons using superconductor - normal metal tunnel junctions, Phys. Rev. Lett. 92, 056804 (2004).
3. Savin A. M., Pekola J.P., Flyktman J.T., Anthore A., and Giazotto F., Cold electron Josephson transistor, Appl. Phys. Lett. 84, 4179 (2004).
4. Giazotto, F., and Pekola, J.P., Josephson tunnel junction controlled by quasiparticle injection, Journal of Applied Physics, 97, p. 023908/1-4 (2005).
5. Giazotto, F., Heikkila, T., Luukanen, A., Savin, A., and Pekola, J., Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications, Reviews of Modern Physics, 78, p. 217-274 (2006).
Project # 9:
6. Kivioja, J.M., Nieminen, T.E., Claudon, J., Buisson, O., Hekking, F.W.J., and Pekola,J., Weak coupling Josephson junction as a current probe: effect of dissipation on escape dynamics, New Journal of Physics, 7, 179, p. 1-21 (2005).
7. Kivioja, J.M., Nieminen, T.E., Claudon, J., Buisson, O., Hekking, F.W.J., and Pekola, J., Observation of transition from escape dynamics to underdamped phase diffusion in a Josephson junction, Physical Review Letters, 94, p. 247002/1-4 (2005).
8. Hekking, F.W.J. and Pekola, J., Finite frequency quantum noise in an interacting mesoscopic conductor, Physical Review Letters, 96, p. 056603/1-4 (2006).
9. Brosco V., Fazio R., Hekking F.W.J., and Pekola J.P., cond-mat/0603844, submitted.
10. M?tt?nen M., Pekola J.P., Vartiainen J.J., Brosco V., and Hekking F.W.J., cond-mat/0604198, submitted.
11. Bunkov Yu.M., L'vov V.S., and Volovik G.E., Solution of the problem of catastrophic relaxation of homogeneous spin precession in superfluid 3He-B, submitted to Journal of Experimental and Theoretical Physics Letters (2006).
Projects #13, # 15, #16, #17, and #22
12. de Graaf R.17, Solntsev R.E., Chagovets T.22, Zmeev D., Blaauwgeers R.16, Eltsov V.B., Haley R.P.15, and Krusius M, Can the onset of superfluid turbulence be expressed with scaling laws?, abstract submitted to the International Conference on Quantum Gases, Fluids, and Solids 2006, Kyoto, Japan, 7 July – 8 Aug, 2006; and to be published.
13. Blaauwgeers R.16, Blazkova M.22, Clovecko M.22, Eltsov V.B., de Graaf R.17, Hosio J., Krusius M., Schmoranzer D., Schoepe W.13, Skrbek L.22, Skyba P., Solntsev R.E., and Zmeev D.E., Quartz tuning fork: Thermo-meter, pressure- and viscometer for helium liquids, Journal of Low Temperature Physics, submitted (2006).
14. de Graaf R., Solntsev R.E., Eltsov V.B., Kopu J., and Krusius M., Wall-mediated vortex instability in applied flow and the onset of turbulence in rotating superfluid 3He-B, abstract submitted to the International Conference on Quantum Gases, Fluids, and Solids 2006, Kyoto, Japan, 7 July – 8 Aug, 2006, to be published in the conference proceedings in Journal of Low Temperature Physics (2007).
15. Solntsev R.E., de Graaf R., Eltsov V.B., and Krusius M., Dynamic remnant vortices in superfluid 3He-B, abstract submitted to the International Conference on Quantum Gases, Fluids, and Solids 2006, Kyoto, Japan, 7 July – 8 Aug, 2006, to be published in the conference proceedings in Journal of Low Temperature Physics (2007).
Project # 18:
16. Todoshchenko, I., Alles, H., Junes, H., Parshin, A., and Tsepelin, V., Measurements on the surface tension of 3He crystals near 100 mK, Journal of Low Temperature Physics, 138, 3/4, p. 811-816 (2005).
Projects # 24 and #14:
17. Lindell, R.K., Sillanpaa, M.A., Heikkila, T.T., Delahaye, J.14, Yamaguchi, T., Sonin, E.B.24, and Hakonen, P.J., Small Josephson junction as detector of non-Gaussian noise, in Conference Proceedings of "Unsolved problems of noise and fluctuations": UPoN 2005, AIP Conference Proceedings 800, p. 563-568 (2005).
18. Hakonen, P.J., Paila, A., and Sonin, E.B., Statistics of electron tunneling in normal tunnel junctions, cond-mat/0604479, submitted to Journal of Low Temperature Physics.
The ULTI Large-Scale Facility offers expertise and equipment for outside users to undertake measurements at temperatures from 4 Kelvin down to the lowest attainable. The installation is located in the Low Temperature Laboratory (LTL) of the Helsinki University of Technology (TKK). ULTI, a continuation of ULTI III, will contribute to scientific progress and technical development of ultra low temperature physics in Europe, to serve as a first-rate educational center for young physicists, and to act as a node for scientific collaboration between Russia and the EU countries. The in-house research includes experimental programs on refrigeration and cryogenics in the liquid-helium range and below and experimental and theoretical studies of quantum fluids and solids, nuclear magnetism, and electrical transport in normal and superconducting structures of nanometer size. Equipment for high-precision optical interferometry at low temperatures and electron beam lithography for making nanosize samples are available as well.
The low temperature and nanophysics section of the LTL consists of about 35 persons, of whom 10 are senior scientists. The ULTI refrigeration equipment includes three sub-millikelvin cryostats, each with a 3He/4He dilution refrigerator for precooling a copper nuclear demagnetization stage. One apparatus can be rotated around its vertical axis up to 40 rev/min, Another is a cascade refrigerator, with two nuclear cooling stages in series, which holds the current low temperature world record of 100 picokelvin. Three smaller cryostats are available for mesoscopic studies down to 50 millikelvin temperatures.
Researcher and students interested in experiments at ultra low temperatures, please contact:
Prof. Mikko Paalanen
Low Temperature Laboratory
Helsinki University of Technology
P.O. Box 2200
Phone: +358-9-451 2957
Fax: +358-9-451 2969