engleski

Spin and charge order in Hg1201

We describe the Hg1201 cuprate in the pseudogap (PG) phase from a 3-band Fermi liquid point of view. The PG is modeled by a k-dependent gap parameter ∆(k), conforming with experiment. Susceptibilities are evaluated in the low- temperature metallic state without further renormalisation by interactions. The effect of strong correlations in the 2D metal is studied by coherent kinematic factors, originating from setting the Hubbard Ud→∞ [1]. The magnetic susceptibility shows a Y-shaped transverse spin response much like the recent experimental results [2] in the PG phase of Hg1201. The response is suppressed below the commensurate peak at ω = 2 ∆0. The strongly anisotropic gap ∆(k) extends the non-dispersive vertical part of the Y-shape, as seen in experiment. (Using an isotropic gap yields a very short vertical part, making the response more V- shaped.) At higher frequencies it displays isotropic upward branches from interband excitations. The SDW gap ∆(k), assumed to open at T∗ ≈ 300 K, reconstructs the Fermi surface, leaving only a pocket around the nodal points. The bands at T(CDW) << T∗ nest to give a qCDW of around 0.28 r.l.u., as observed [3]. Such a gapped Fermi liquid scenario suffices to understand the charge and spin responses of underdoped Hg1201 in the experimentally observed hierarchy. The kinematic correlations caused by a large Ud change the Y- response towards the ”hourglass” X-shape, thus replacing the peak at ω = 2 ∆0 and q = QAF with incommensurate downward branches. This result indicates that effects of strong-coupling correlations at the Fermi surface are more significant in the lanthanum than in the mercury cuprates.

high Tc; cuprates; antiferromagnetism; pseudogap; neutron scattering

Rad je kao poster prikazan na skupu International School and Workshop on Electronic Crystals (ECRYS-2014), održanom od 11-23.08.2014.g., Cargese, Francuska