Reaserch On Aromatic Superconductors

Enormous attention has been drawn to the organic superconductors because they are predicted to have high T_c,and the pairing mechanism may be unconventional.Among the organic superconductor families,aromatic superconductors have become a hot topic in the field of organic superconductors in recent years.On one hand,because of the different combinations of benzene rings and the family of aromatic hydrocarbon is very huge.They are potential candidates for high T_c superconductors.On the other hand,superconductivity can be achieved simply by doping alkali,alkali-earth or rare earth metals in a certain proportion.Some of these superconductors have novel physical phenomena such as the positive correlation between T_C and pressure,which is also the reason why aromatic superconductors are concerned.It is very important to explore the new type of aromatic superconductors and understand its intrinsic physical phenomena.In the first chapter of this dissertation,the history of organic superconductivity and the classification of organic superconductors are introduced.Then the development of superconductivity theory is briefly reviewed,including the G-L theory and the BCS theory.Lastly,the progress of theoretical research on aromatic superconductors is also introduced.In the second chapter,the experimental methods of synthesis of aromatic superconductors are introduced,such as solid state reaction method and solution method.Then,the experimental instruments to measure the magnetization,resistance and composition of superconducting materials are introduced.In Chapter 3,we report the synthesis of a new aromatic superconductor Sm₃1,3,5-triphenylbenzene by solid state reaction.Sm means samarium,which is a rare earth metal.The space group of the sample is P2/m as determined fom the fitting to the XRD data.The T_c of the sample is 4.3 K.Based on rough calculation,the superconducting shielding fraction of the sample is about 1%,which is consistent with the previous report that the superconducting volume of organic aromatic superconductors are all small.The hysteresis loops reveal that the Sm₃1,3,5-triphenylbenzene is a typical type II superconductor.We draw the H-T phase diagram of the sample based on the magnetization data,and fit the H_c1-T phase line based on the G-L theory.we find that the fitting is very well.Based on the fitted equation,we calculated the H_c1 which is 126Oe when T approaches 0 K.We can't fit H_c2-T phase line,so we can't get H_c2?0?when T equals 0 K.However,we can roughly estimate that H_c2?0?should be quite high at 0K.Chapter four gives a detailed summary of the whole dissertation.