The appearance of superconductivity at ambient pressures in the undoped iron pnictide parent compound SrFe2As2 is studied experimentally using several techniques and approaches to aid in understanding the nature of this phase. Low temperature magnetization measurements of single crystals of SrFe2As2 reveal diamagnetic screening due to the onset of superconductivity below 21 K, with volume fract...

—At high nuclear density and small temperature due to the asymptotic freedom property of QuantumChromoDynamics and to the existence of an attractive channel in the color interaction, diquark condensates might be formed. Since these condensates break the color gauge symmetry, this phenomenon has the name of color superconductivity. In the last few years this has become a very active field of res...

Unconventional Superconductors Many novel superconductors show properties different from standard superconductors (overview); Aim of this lecture: • discuss structure of Cooper pairs from a symmetry point of view key symmetries: time reversal and inversion symmetry • learn the techniques of the phenomenological approach: generalized Ginzburg-Landau theories broken symmetries and order parameter...

The discovery of superconductivity in iron pnictides has attracted considerable interest of the condensed matter physics community [1]. The superconductivity has been observed in both 1111 and 122 system. These superconductors display a fascinating interplay between magnetism and superconductivity. Two kinds of techniques are mainly performed to study these materials. One is the neutron scatter...

Quantum-mechanical fluctuations in strongly correlated electron systems cause unconventional phenomena such as non-Fermi liquid behavior, and arguably high temperature superconductivity. Here we report the discovery of a field-tuned quantum critical phenomenon in stoichiometric CeCu(2)Ge(2), a spin density wave ordered heavy fermion metal that exhibits unconventional superconductivity under ≃10...

We study theoretically competition between the charge ordering and the superconductivity in the two-dimensional organic conductor β-(meso-DMBEDT-TTF)2PF6. We analyze the extended Hubbard model on a weakly-dimerized lattice based on the random phase approximation and Eliashberg equations. We found the reentrant behavior of the checkerbord-type charge-ordered phase in the phase diagram, and the t...

Experimental studies of superconductivity properties of fullerides are briefly reviewed. Theoretical calculations of the electron-phonon coupling, in particular for the intramolecular phonons, are discussed extensively. The calculations are compared with coupling constants deduced from a number of different experimental techniques. It is discussed why the A3C60 are not Mott-Hubbard insulators, ...

Single crystals of novel orthorhombic (space group Pnnm) iron tetraboride FeB4 were synthesized at pressures above 8 GPa and high temperatures. Magnetic susceptibility and heat capacity measurements demonstrate bulk superconductivity below 2.9 K. The putative isotope effect on the superconducting critical temperature and the analysis of specific heat data indicate that the superconductivity in ...

Intermetallic compounds containing f-electron elements display a wealth of superconducting phases, that are prime candidates for unconventional pairing with complex order parameter symmetries. For instance, superconductivity has been found at the border of magnetic order as well as deep within ferroand antiferromagnetically ordered states, suggesting that magnetism may promote rather than destr...