Akio Tsukada

Magnetic penetration depth measurements of Pr2-xCexCuO4-delta films on buffered substrates: evidence for a nodeless gap.

We report measurements of the inverse squared magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-delta) (0.115< or =x < or =0.152) superconducting films grown on SrTiO3 (001) substrates coated with a buffer layer of insulating Pr2CuO4. lambda(-2)(0), T(c), and normal-state resistivities of these films indicate that they are clean and homogeneous. Over a wide range of Ce doping, 0.124< or =x < or =0.144, lambda(-2)(T) at low T is flat: it changes by less than 0.15% over a factor of 3 change in T, indicating a gap in the superconducting density of states. Fits to the first 5% decrease in lambda(-2)(T) produce values of the minimum superconducting gap in the range of 0.29< or =Delta(min)/k(B)T(c)< or =1.01.

Emerging superconductivity hidden beneath charge-transfer insulators

In many of todays most interesting materials, strong interactions prevail upon the magnetic moments, the electrons, and the crystal lattice, forming strong links between these different aspects of the system. Particularly, in two-dimensional cuprates, where copper is either five- or six-fold coordinated, superconductivity is commonly induced by chemical doping which is deemed to be mandatory by destruction of long-range antiferromagnetic order of 3d9 Cu2+ moments. Here we show that superconductivity can be induced in Pr2CuO4, where copper is four-fold coordinated. We induced this novel quantum state of Pr2CuO4 by realizing pristine square-planar coordinated copper in the copper-oxygen planes, thus, resulting in critical superconducting temperatures even higher than by chemical doping. Our results demonstrate new degrees of freedom, i.e., coordination of copper, for the manipulation of magnetic and superconducting order parameters in quantum materials.

Superconductor-to-metal quantum phase transition in overdoped La2−xSrxCuO4

We investigate

In situ angle-resolved photoemission study of MBE-grown (La,Ce)2CuO4 thin films

T_c

Three-dimensional superconductivity of the structurally two-dimensional superconductor La1.87Y0.13CuO4: study of an angle-dependent critical current density

and magnetic penetration depth

Generic phase diagram of “electron-doped” T′ cuprates

\lambda (T)

Synthesis and properties of superconductingT′−R2CuO4(R=Pr, Nd, Sm, Eu, Gd)

near the superconductor-metal quantum phase transition in overdoped

Absence of18anomaly in strained thin films ofLa2−xBaxCuO4+δ

La_{2-x}Sr_{x}CuO_{4}

Superconductivity in undoped T’-RE2CuO4 with Tc over 30 K

films. Both

Reduction dependence of superconductivity in the end-member T' cuprates

T_c