Crystal Structure And Superconducting Properties Of Metal Doping Aromatic Hydrocarbon Organic Materials

Superconductivity discovered in 1911 has attracted considerable attention.Searching new superconducting materials and understanding their superconducting mechanism are the hot research topics in the condensed matter physics community,due to its extensive application prospects in energy,information,military and medicine.In 2010,Y.Kubozono et al found supercouductivity at 18K in potassium-doped picene.In recent years,many aromatic hydrocarbon superconductors have been preparated by doping alkali meatl,alkaline-earth metals and rare-earth metal into polycyclic aromatic hydrocarbons.In this thesis,potassium doped phenanthrene,p-terphenyl have been synthesized by using the high vaccum annealing method.The crystal structure,molecular vibration,and magnetic property are characterized by using X-ray diffraction,Raman scattering,and superconducting quantum interference devices?SQUID?.The main results are as follows:1:A new molecular crystal of potassium-doped phenanthrene was synthesized by the high vaccum annealing method.XRD spectra showed that the crystallization is affected strongly by annealing temperature and cooling rate,and a very slow cooling rate is required to grow the crystal along the[001]direction.The combination of measured and calculated X-ray diffraction peaks indiacted that two K atoms are intercalated in intralayer and one K atom intercalated in interlayer,leading to an expansion of c-axis.The first principles calculations showed that the synthesized crysal lies in metallic state,which can form a superconducting state by considering the electron-phonon interaction.Oue findings provide an important basis for the synthesis of metal-doped molecular crystal and the observed superconductivity in potassium-doped phenanthrene.2:The sample of potassium-doped p-terphenyl has been grown by the high vaccum annealing method.The combination of X-ray diffraction spectrum and Raman spectrum shows that besides potassium-doped p-terphenyl and KH,there exist C₆₀ and graphite in annealed sample,which are found for the first time in the metal-doped aromatic hydrocarbon.The red-shifts of partial peaks of p-terphenyl in Raman spectrum demonstrate that 4 s electron of doped potassium is transferred to C atom.We found that Curie paramagnetic behaviors are observed for most of samples in the whole temperature region.On the other hand,in one of the samples annealed at 260?,there exist three anomalous sharp decreases at 17.86,10.00 and 6.42 K in the zero-field cooling magnetic measurement.It is reasonable to attribute the anomalous sharp decrease at 17.86 K to being produced by potassium-doped C₆₀,while the anomalous sharp decreases at 10.00 and 6.42 K,which have not been reported yet,may be produced by potassium-doped p-terphenyl.Our results are useful for understanding the physical properties of metal-doped aromatic hydrocarbons.Furthermore,our findings provide a new routine to synthesize C₆₀ and graphite at low temperature.