High Pressure Nuclear Magnetic Resonance Studies of the CeRhIn5 Heavy Fermion Superconductors

We report nuclear magnetic resonance (NMR) data for 115In(1) and 115In(2) sites in the heavy fermion superconductor CeRhIn5 under hydrostatic pressure. The pressure dependence of the static NMR Knight shift can influence electronic structure in CeRhIn 5, such as a suppression of the hyperfine coupling to the In(1) site, and a discontinuous change of electric field gradient function at the In(2) at quantum critical point (Pc1 = 1.75GPa). Another high pressure NMR phenomenon called Knight shift anomaly indicates that the heavy fermion coherence temperature increases from 18K at ambient pressure to 36K by 2GPa, reflecting an increase in hybridization between conduction electrons and the Ce 4f electrons as this system crosses the quantum critical point.;We also report the latest idea and the progress of our designer anvil surface coil in the diamond anvil cell. A parallel set of tungsten microcoil with diameters from 650mum to 950mum is fabricated and embedded on the diamond culet. The field density distribution of this coil is simulated, and the 27Al NMR signal is successfully detected. In addition, the signal-to-noise ratio study on several types of pressure cells with various P ranges implies the maximum possible and allowable pressure limit to be achieved, which may enlighten the high pressure NMR community to expand the capability on these instruments.