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Superconductivity Precursor “Para-Magnetic” Effect

#A-939


Investigation of the “Para-Magnetic” Effect as Precursor to the Superconductivity (by Means of the Single-Layer Flat Coil-Based Test Method of High Spatial-Resolution to be Created)

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • INS-MEA/Measuring Instruments/Instrumentation

Status
3 Approved without Funding

Registration date
09.10.2002

Leading Institute
Institute for Physical Research, Armenia, Ashtarak-2

Supporting institutes

  • Yerevan State University, Armenia, Yerevan

Collaborators

  • University of Twente / Department of Applied Physics, The Netherlands, Enschede\nUniversidade de Lisboa / Center for Nuclear Physics, Portugal, Lisbon\nUniversity of Waterloo, Canada, ON, Waterloo\nTohoku University / Institute for Materials Research (IMR), Japan, Sendai\nUniversity of Toronto / Faculty of Pharmacy, Canada, ON, Toronto\nUniversity of Wisconsin-Madison / Applied Superconductivity Center, USA, WI, Madison\nUniversite de Caen / Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, France, Caen

Project summary

The aim of the Project is revealing of physical processes determining real shape (specified by the “Para-Magnetic” effect) of the normal-to-superconductive (N/S) phase transition curve, as well as establishing relation between the shape of transition curve and normal-state physical characteristics of the matter. For that purpose, Open-Flat Coil-based highly sensitive new test technique (the OFCmagnetometer) will be developed and used as a crucial research instrument. As a result of the Project execution, a radically new type visualizing method will be developed too (using a focused laser beam as a probing signal), capable of imaging the superconducting properties (in particular, the 2D current distribution) of thin high-Tc superconductive (HTS) materials, with about 1-2µm spatial-resolution, enabling to identify also localized defects over sub-mm size thin plate-like HTS material. Re-orientation of the unique equipments and scientific personnel, involved before in defense problems, into the area of civil research programs also enters into the aim of the present project.

With this aim we plan to study superconductivity (SC) at the temperatures close to the phase transition – the fluctuation region (the start of the superconducting carriers’ formation). More concrete, a new “Para-Magnetic” (PM) effect detected in superconductors recently (S.G. Gevorgyan et al., “New paramagnetic peculiarity of the superconductive transition detected by a highly sensitive OFC-magnetometer”, Supercond. Sci. Technol., 14 (2001) 1009-1013) as well as the consequences caused by this weakly expressed phenomenon and following from the analysis of the shape of N/S transition curve, should be thoroughly investigated. At that, in particular, we plan to establish the nature of influence of the structural changes as well as SC material’s crystalline-structure defects and impurities on the observed PM effect. This study will cover a noticeable part of the investigation. For this purpose we intend to synthesize the HTS materials with different impurity-defect compositions.

The new PM effect precedes the stronger expressed “Dia-Magnetic” (DM, “Meissner”) ejection and fills up the shape of N/S transition curve, which seems is more complicated than it was known. It is specifying fine details of superconductive phase transition. We believe this effect will contribute to the final understanding of the nature of superconductivity in future. However, even now, seems the ‘Para-Magnetic’ effect creates grounds to separate each other the “ideal conductive” (the state without resistance) and the “superconductive” (the ‘Meissner’ state) phase transitions, and enables to connect the shape of the transition curve with some important normal-state physical characteristics of the superconductive matter.

Further investigations in this area may improve our understanding of the role and behavior of superconducting carriers (so-called “Cooper” pairs) in superconductive materials, which can promote revealing of the nature of superconductivity in high-Tc superconductors. The preliminary test results, obtained in this study, demonstrate wide perspectives of the single-layer flat coil-based MHz-range new testing method to provide such a study.

The urgency of the problem is conditioned by the need to study weakly expressed physical effects in superconductors, particularly in HTS, at the temperatures very close to the N/S phase transition (at the beginning of ‘Cooper’ pairs’ formation). This is possible, if superconductive state is investigated by non-destructive and sensitive new test-methods with a high spatial resolution, especially close to the phase transition, enabling to study also small-volume (clean) specimens with small signals. Such methods are of prime importance not only for clarification of the problems in basic superconductivity. We need their help also for observation of a defect structure and 2D current distribution inside highTc superconductors. Such a visualizing technique may enable to reveal the main reasons and mechanisms of the current limitations in thin films. Further studies by use of this type technique, better if combined with the Magneto-Optical Imaging system, may bring similar new results also in industrial superconductors of various compositions (HTS tapes, coated conductors, etc.). This type of technique can be used also in many other fields of modern Science and Technology.

Despite of large progress in understanding of the high-Tc superconductors’ atomic structure and physical properties since their discovery [1], nevertheless, the microscopic nature of superconductivity in these materials is not revealed yet [2-4]. One of the reasons is lack of test-methods for many-sided and non-destructive study of the physics of N/S transition in HTS with high resolution, particularly, at the temperatures close to the phase transition (at the start of formation of the superconductive state). However, the problem is not only in an insufficient sensitivity of the existing test-devices in this relatively narrow temperature range, close to Tc. We deal also with some “open” questions in basic superconductivity area (relating with low-Tc (“helium”) superconductors (LTS) too) details see in the next section. The answers on questions need thorough investigation of the physics of N/S phase transition in a strongly correlated system of electrons (‘Cooper’ pairs) created at the moment of the transition. Detected recently ‘Para-Magnetic’ effect demonstrates and confirms the existence of fine physics near Tc to be investigated thoroughly during the execution of this project. The test method, which could extract it, may enable to discover other weakly expressed physical phenomena too, at the transition. It is under many-sided development at present. The method is capable of 2D imaging of superconductive properties in thin flat HTS materials. There are ways to improve the method’s performance to be realized. How better will we understand the physics of superconductivity after arriving to the answers of the problems discussed in details below, and what are the key advantages of the present technique, capable of revealing fine details of the superconductive phase transition, we are going to discuss in the next sections of the proposal below.

The achievement of the Project goals is quite real due to enough experience of the Project principal and participants in the field of superconductivity, as well as because of the obtained large preliminary results on above-discussed matter (presented in details below), which serve the basis for the future successful research work in this area.


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