Landau quantization effects in the charge-density-wave system (Per)2M(mnt)2 (where M = Au and Pt)

Quantum oscillations in antiferromagnetic CaFe(2)As(2) on the brink of superconductivity

We report quantum oscillation measurements on CaFe(2)As(2) under strong magnetic fields-recently reported to become superconducting under pressures of as little as a kilobar. The largest observed carrier pocket occupies less than 0.05% of the paramagnetic Brillouin zone volume-consistent with Fermi surface reconstruction caused by antiferromagnetism. On comparing several alkaline earth AFe(2)As(2) antiferromagnets (with A = Ca, Sr and Ba), the dependences of the Fermi surface cross-sectional area F(α) and the effective mass m(α)(*) of the primary observed pocket on the antiferromagnetic/structural transition temperature T(s) are both found to be consistent with the case for quasiparticles in a conventional spin-density wave model. These findings suggest that the recently proposed strain-enhanced superconductivity in these materials occurs within a broadly conventional spin-density wave phase.

Soliton wall superlattice in the quasi-one-dimensional conductor (Per)(2)Pt(mnt)(2)

We suggest a model to explain the appearance of a high resistance high magnetic field charge-density-wave (CDW) phase, discovered by Graf et al. [Phys. Rev. Lett. 93, 076406 (2004)10.1103/PhysRevLett.93.076406] in (Per)(2)Pt(mnt)(2), where Per is perylene and mnt is maleonitriledithiolate molecules. In particular, we show that the Pauli spin-splitting effects improve the nesting properties of a realistic quasi-one-dimensional electron spectrum and, therefore, a high resistance Peierls CDW phase is stabilized in high magnetic fields. In low and very high magnetic fields, a periodic soliton wall superlattice (SWS) phase is found to be a ground state. We suggest experimental studies of the predicted phase transitions between the Peierls and SWS CDW phases in (Per)(2)Pt(mnt)(2) to discover a unique SWS phase.