Quantum-Critical Spin-Density Waves in Iron-Selenide High-Tc Superconductors

Abstract

Hidden spin-density waves (hSDW) with Neel ordering vector (pi,pi) have been proposed recently as parent groundstates to electron-doped iron-selenide superconductors. Doping such groundstates can result in visible electron-type Fermi surface pockets and faint hole-type Fermi surface pockets at the corner of the folded Brillouin zone. A Cooper pair instability that alternates in sign between the electron-type and the hole-type Fermi surfaces has recently been predicted. The previous is due to the interaction of electrons and holes with hidden spin fluctuations connected with hSDW order that is near a quantum-critical point. Quantum criticality is tuned in by increasing the strength of Hund's Rule from the hSDW state. We find that the exchange of hidden spin fluctuations by electrons/holes in the critical hSDW state results in asymptotic freedom. In particular, the strength of spin-flip interactions becomes weaker and weaker on length scales that are shorter and shorter compared to the range of hSDW order. We then argue that string states that connect well-separated particle/hole excitations in the hSDW are robust. This suggests a picture where the hole degrees of freedom mentioned previously are confined.

19 pages, 6 figures

References in corpus (5)

• Spin-triplet p-wave pairing in a 3-orbital model for iron pnictide superconductors
• Sign-problem-free quantum Monte Carlo of the onset of antiferromagnetism in metals
• Spin resonance in the superconducting state of Li${}_{1-x}$Fe${}_x$ODFe${}_{1-y}$Se observed by neutron spectroscopy
• Low ordered magnetic moment by off-diagonal frustration in undoped parent compounds to iron-based high-Tc superconductors
• Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order