We report a coexistence of superconductivity and antiferromagnetism in five-layered compound HgBa2Ca4Cu5Oy (Hg-1245) with Tc = 108 K, which is composed of two types of CuO2 planes in a unit cell; three inner planes (IP's) and two outer planes (OP's). The Cu-NMR study has revealed that the optimallydoped OP undergoes a superconducting (SC) transition at Tc = 108 K, whereas the three underdoped IP's do an antiferromagnetic (AF) transition below TN ∼ 60 K with the Cu moments of ∼ (0.3 − 0.4)µB . Thus bulk superconductivity with a high value of Tc = 108 K and a static AF ordering at TN = 60 K are realized in the alternating AF and SC layers. The AF-spin polarization at the IP is found to induce the Cu moments of ∼ 0.02µB at the SC OP, which is the AF proximity effect into the SC OP.

We report a site selective Cu-NMR study on underdoped Hg-based five-layered high-Tc cuprate HgBa2Ca4CU5O(12+delta) with a Tc = 72 K. Antiferromagnetism (AFM) has been found to take place at T(N) = 290 K, exhibiting a large antiferromagnetic moment of 0.67-0.69 microB at three inner planes (IP). This value is comparable to the values reported for nondoped cuprates, suggesting that the IP may be in a nearly nondoped regime. Most surprisingly, the AFM order is also detected with M(AFM)(OP) = 0.1 microB even at two outer planes (OP) that are responsible for the onset of superconductivity (SC). The high-Tc SC at Tc = 72 K can uniformly coexist on a microscopic level with the AFM at OP's. This is the first microscopic evidence for the uniform mixed phase of AFM and SC on a single CuO2 plane in a simple environment without any vortex lattice and/or stripe order.

There is a soliton in a superconductor having two bands (two-band superconductor), when the interband interaction is much smaller than the intraband interaction. This soliton is in a stable state. In the soliton the relative phase between two gap parameters rotates 0 to 2pi (or -pi to pi), where each gap resides in each band. A phase slip of the superconducting order parameter is accompanied with the soliton. The phase slip is not nx2pi where n is an integer. A soliton traps the flux inside the superconducting ring, of which magnitude is not integral multiples of the fluxoid quantum.