Kohei Yoshimatsu

Reversible superconductor-insulator transition in LiTi2O4 induced by Li-ion electrochemical reaction.

Transition metal oxides display various electronic and magnetic phases such as high-temperature superconductivity. Controlling such exotic properties by applying an external field is one of the biggest continuous challenges in condensed matter physics. Here, we demonstrate clear superconductor-insulator transition of LiTi2O4 films induced by Li-ion electrochemical reaction. A compact electrochemical cell of pseudo-Li-ion battery structure is formed with a superconducting LiTi2O4 film as an anode. Li content in the film is controlled by applying a constant redox voltage. An insulating state is achieved by Li-ion intercalation to the superconducting film by applying reduction potential. In contrast, the superconducting state is reproduced by applying oxidation potential to the Li-ion intercalated film. Moreover, superconducting transition temperature is also recovered after a number of cycles of Li-ion electrochemical reactions. This complete reversible transition originates in difference in potentials required for deintercalation of initially contained and electrochemically intercalated Li+ ions.

Epitaxial growth and electric properties of γ-Al2O3(110) films on β-Ga2O3(010) substrates

Epitaxial growth and electrical properties of γ-Al2O3 films on β-Ga2O3(010) substrates were investigated regarding the prospect of a gate oxide in a β-Ga2O3-based MOSFET. The γ-Al2O3 films grew along the [110] direction and inherited the oxygen sublattice from β-Ga2O3 resulting in the unique in-plane epitaxial relationship of γ-Al2O3 ∥ β-Ga2O3[001]. We found that the γ-Al2O3 layer had a band gap of 7.0 eV and a type-I band alignment with β-Ga2O3 with conduction- and valence-band offsets of 1.9 and 0.5 eV, respectively. A relatively high trap density ( 2 × 1012 cm−2 eV−1) was found from the voltage shift of photoassisted capacitance–voltage curves measured for a Au/γ-Al2O3/β-Ga2O3 MOS capacitor. These results indicate good structural and electric properties and some limitations hindering the better understanding of the role of the gate dielectrics (a γ-Al2O3 interface layer naturally crystallized from amorphous Al2O3) in the β-Ga2O3 MOSFET.

Impact of built-in potential across LaFeO3/SrTiO3 heterojunctions on photocatalytic activity

Polar-nonpolar interfaces between insulating LaFeO3 (LFO) and semiconducting SrTiO3 (STO) were investigated to elucidate effects of built-in potential on photocarrier dynamics during water oxidation reactions. The LFO films were grown on the TiO2- and SrO-terminated (001) Nb-doped STO substrates by using pulsed-laser deposition. The photocurrent-voltage curves varied depending on the interface termination. Potential profiles across the interface were established from these curves as well as capacitance-voltage curves. The presence of a depletion (accumulation) region near the SrO- (TiO2-) terminated interface facilitates (suppresses) the extraction of photocarriers generated in STO. On the other hand, the difference in the built-in potential in LFO barely reflects the magnitude of the photocurrent.

Thickness-dependent magnetic properties and strain-induced orbital magnetic moment inSrRuO3thin films

Thin films of the ferromagnetic metal

Photoemission and x-ray absorption studies of the isostructural to Fe-based superconductors diluted magnetic semiconductor Ba 1 − x K x ( Zn 1 − y Mn y ) 2 As 2

{\mathrm{SrRuO}}_{3}

Microwave Effects on Co–Pi Cocatalysts Deposited on α-Fe2O3 for Application to Photocatalytic Oxygen Evolution

(SRO) show a varying easy magnetization axis depending on the epitaxial strain, and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on

Formation of indium–tin oxide ohmic contacts for β-Ga2O3

{\mathrm{SrTiO}}_{3}

Thickness-dependent ferromagnetic metal to paramagnetic insulator transition inLa0.6Sr0.4MnO3thin films studied by x-ray magnetic circular dichroism

(001) substrates by soft x-ray magnetic circular dichroism at the Ru

Origin of the Anomalous Mass Renormalization in Metallic Quantum Well States of Strongly Correlated Oxide SrVO_{3}.

{M}_{2,3}

Photoemission and DMFT study of electronic correlations in SrMoO3: Effects of Hund's rule coupling and possible plasmonic sideband

edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to nonmagnetic at around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be