Spectroscopic measurements of Zeeman splitting of the density of states in high temperature superconducting tunneling junctions

We report c-axis tunneling spectroscopy investigations in high magnetic fields (I-V characteristics and tunneling conductance dI/dV) of high quality planar junctions fabricated from c-axis oriented NdBa2Cu3O7–delta/PrBa2Cu3O7–delta/NdBa2Cu3O7–delta thin film multilayers. The tunneling conductance in a parallel magnetic field reveals Zeeman splitting of the quasiparticle density of states. In the presence of spin-orbit interactions, our measurements for the tunneling density of states and the tunneling conductance show a spin splitting of gµBH in energy space of the density of states peak. Here the quantity µB is the Bohr magneton, g is the g factor of the electron, and H is the applied magnetic field. The magnitude of the splitting is attributed to the magnetic moment of the quasiparticles. The spin splitting of the density of states in HTS multilayer tunneling junctions could be used as a very powerful technique to determine the relative spin polarization in magnetic materials.