טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGil Drachuck
SubjectExperimental Investigation of the Mechanism for High
Temperature Superconductivity Using Single
Crystals of CLBLCO
DepartmentDepartment of Physics
Supervisor Full Professor Keren Amit
Full Thesis textFull thesis text - English Version


Abstract

We report the successful growth of a (CaxLa1-x)(Ba1.75-xLa0.25)Cu3Oy CLBLCO single crystal. In this material, x controls the maximum of Tc (Tcmax), with minimal structural changes.  Therefore, it allows a search for correlations between material properties and Tcmax  We demonstrate that the crystals cleave well This thesis is present a collection of three experimental research papers in the field of high temperature enough for Raman scattering, ARPES and recently resonant inelastic x-ray scattering (RIXS), and has opened new possibilities for cuprate research.


We also present ARPES data from CLBLCO. We find that the surface doping is independent of the bulk doping or the Ca to Ba ratio. We also demonstrate that the gap can be measured in this system. The hopping parameter t is larger for x = 0.4 than for x = 0.1 in the overdoped sides. This suggests that Tcmax is correlated with electron-orbital overlaps on neighboring sites.


In addition, we investigated the newly discovered nodal gap in hole doped cuprates using a single crystal of antiferromagnetic La2-xSrxCuO4. We performed angle resolved photoemission spectroscopy measurements as a function of temperature a nodal gap bellow 45K. muSR measurements ensured that

the sample is indeed antiferromagnetic and that its doping is x=1.92, which is below the spin glass phase boundary. We also performed neutron diffraction measurements and determined the thermal evolution of the commensurate and incommensurate magnetic order. Our major finding is that a nodal gap opens at a temperature well below the commensurate ordering at 140K, and close to the incommensurate spin density wave ordering temperature of 30K.