We try to understand quantum nature of materials. Quantum effect is more clearly manifested in some exotic material systems such as high-Tc cuprate superconductors and the quantum Hall systems. In the high-Tc cuprates, strong electron correlation is the key factor, which is believed to determine all the novel properties in both superconducting and normal states. Even though a consensus about its gap symmetry, which is d-wave is reached, the superconducting mechanism of high-Tc cuprate superconductors is still elusive now. The high Tc and d-wave gap symmetry suggest that superconducting mechanism may unconventional. The problem of high-Tc cuprates is one of the long-standing puzzles in physics even in 21 century. On the other hand, the quantum Hall effect introduces the concept of "topology" in mathematics to solid state physics, and first showed that topology is the key tool to distinguish symmetrically same states of matters. Before this discovery, the symmetry breaking and accompanying Landau theory had provided the conceptual basis to classify states of matters. However, the Landau theory is a framework unable to distinguish symmetrically same states of matters but topologically distinct states. Thus, implications of quantum Hall effect is far-reaching, making significant impact on modern condensed matter physics and changing fundamental viewpoint of physics. This discovery ignites rise of topological insulators and topological metals, which are actively being studied at present.
Our experimental approach is to synthesis new materials in various forms and to characterize them by using diverse experimental techniques. Currently, we grow thin films by using pulsed laser deposition (PLD) techniques and study not only their growth mechanisms but also their chemical and physical properties. We have a state-of-art PLD system with a high vacuum chamber and an excimer laser system. We also have cryo-free superconducting magnet system with a variable temperature insert. In this system, the magnetic field can be varied between - 9 T and + 9 T and the temperature can be changed between 1.7 K and 350 K. In this system, we are able to measure resistivity, magnetoresistance, and Hall effect at different temperatures. We will extend its functionality in near future so that thermal transport, specific heat and angle dependent measurements will be possible. We will also increase our ability of material synthesis to be able to synthesize single crystals and nano-structured materials with novel physics and functionality.