Seminars Archive

Spin density wave state and its influence on material properties

Abstract
Spin density wave (SDW) state is an antiferromagnetic ground state of metals, where the density of conduction electron spins shows spatial modulation. Recent studies show that suppression of SDW phase via chemical substitution or pressure leads to quantum criticality and/or superconductivity. We have studied electronic structure in Vanadium (V)-doped Chromium (Cr) to address quantum criticality and Iron (Fe)-based superconductors to emphasize on magnetism and superconductivity issue using high resolution photoemission spectroscopy. Cr shows SDW transition (TN) at 311 K. Introducing V into Cr reduces the magnetic transition temperature gradually and TN vanishes at about 3.5% doping, which is described as quantum critical point in this system. Experimental results across the quantum critical point in V-doped Cr exhibit signatures of pseudogap and orbital Kondo resonance peak at low temperatures, indicating their relevance in widely discussed quantum phases in correlated electron systems. Fe-based superconductors have drawn much attention during the last decade due to the finding of superconductivity in materials containing a magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested dominant role of d states in their electronic properties, whereas our results reveals that the ligand p states contribution at the Fermi level is found to be much more significant than that indicated in earlier studies. Temperature evolution of the energy bands reveals signature of transition akin to Lifshitz transition in these systems.