Spectroscopy of Novel Materials Group
The Spectroscopy of Novel Materials group uses advanced spectroscopic techniques to study electronic structure, low-energy excitations and correlation effects in a broad range of complex material systems exhibiting surprising and useful properties. These include high-temperature superconductors, low-dimensional magnets, colossal magnetoresistors, topological insulators, oxide thin films, interfaces between oxide materials, and oxide heterostructures. We operate two beamlines with two endstations each.
The SIS beamline offers low-temperature high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES with photon energies in the VUV to soft X-ray regime (10-800 eV). The ADRESS beamline operates in the soft X-ray range (300-1600 eV) and hosts resonant inelastic x-ray scattering (RIXS) and soft x-ray ARPES endstations. Additionally, part of our research makes use of a dedicated pulsed laser deposition (PLD) chamber for in situ studies of thin films, interfaces, and heterostructures. Collectively, these techniques give us the ability to probe surface and bulk properties of complex materials and to visualize the interplay of the electrons with spin, lattice, and orbital degrees of freedom.
PSI scientists have investigated a material that could be suitable for future data storage applications. They have manipulated the crystalline structure of their sample while measuring how this affects the material’s magnetic and electronic properties.
In topological materials, electrons can display behaviour that is fundamentally different from that in ‘conventional’ matter, and the magnitude of many such ‘exotic’ phenomena is directly proportional to an entity known as the Chern number. New experiments establish for the first time that the theoretically predicted maximum Chern number can be reached — and controlled — in a real material.
When magnetism meets topology, colorful novel states can emerge in condensed matter. It is widely believed that parity-time symmetry plays an essential role for the formation of Dirac states in Dirac semimetals. So far, all of the experimentally identified topological nontrivial Dirac semimetals possess both parity and time reversal symmetry. Since the magnetism will break time-reversal symmetry, only in special cases the Dirac states can be protected in a magnetic system. Thus, the realization of magnetic topological Dirac materials remains a major issue in the research of topological physics. In this work, the authors ascertained that the ground state of EuCd2As2 is a good candidate for magnetic topological Dirac semimetal when the spins point in the out-of-plane direction in the A-type antiferromagnetic phase. The Dirac state is protected by the combination of parity-time symmetry with additional translation operation. Moreover, when the spins deviate from out-of-plane direction, the bulk Dirac cone will open a gap, and the system develops into a novel state containing axion insulator, antiferromagnetic topological crystalline insulator, and higher order topological insulator.