Search

We report in-plane resistivity (ρ) and transverse magnetoresistance (MR) measurements for underdoped HgBa2CuO4+δ (Hg1201). Contrary to the long-standing view that Kohler’s rule is strongly violated in underdoped cuprates, we find that it is in fact satisfied in the pseudogap phase of Hg1201. The transverse MR shows a quadratic field dependence, δρ/ρ0=aH², with a(T)∝T-4. In combination with the observed ρ∝T² dependence, this is consistent with a single Fermi-liquid quasiparticle scattering rate. We show that this behavior is typically masked in cuprates with lower structural symmetry or strong disorder effects. [ABSTRACT FROM AUTHOR]

We use neutron scattering to study magnetic excitations near the antiferromagnetic wave vector in the underdoped single-layer cuprate HgBa2CuO4+δ (superconducting transition temperature Tc ≈ 88 K, pseudogap temperature T* ≈ 220 K). The response is distinctly enhanced below T* and exhibits a Y-shaped dispersion in the pseudogap state, whereas the superconducting state features an X-shaped (hourglass) dispersion and a further resonancelike enhancement. A large spin gap of about 40 meV is observed in both states. This phenomenology is reminiscent of that exhibited by bilayer cuprates. The resonance spectral weight, irrespective of doping and compound, scales linearly with the putative binding energy of a spin exciton described by an itinerant-spin formalism. [ABSTRACT FROM AUTHOR]