This review summarizes the progress on basic understanding and applications of volume transport protons in fluorite pyrochlore oxides, discusses present problems challenges ahead.

Flat bands imply lack of itinerancy due to some constraints that, in principle, results anomalous behaviors with randomness. By a molecular orbital (MO) representation the flat band systems, random MO models are introduced where degeneracy is preserved even The zero modes chiral symmetric system sublattice imbalance belong class. After explaining generic construction by MOs, several examples di...

In the first part we study O(N) spins on geometrically frustrated pyrochlore and planar pyrochlore lattices. For classical spins the strong frustration causes a lack of ordering for N 6= 2 at all temperatures. Nevertheless at low temperatures the system is strongly correlated. We find degrees of freedom that are relevant in this regime and find that the correlations are dipolar up to distance ∼...

Abstract. A pyrochlore lattice is considered where the average electron number of electrons per site is half–integer, concentrating on the case of exactly half an electron per site. Strong on-site repulsions are assumed, so that all sites are either empty or singly occupied. Where there are in addition strong nearest–neighbour repulsions, a tetrahedron rule comes into effect, as previously sugg...

Rights: © 2010 American Physical Society (APS). This is the accepted version of the following article: Imamura, N. & Karppinen, Maarit & Yamauchi, H. & Goodenough, J. B. 2010. Magnetic properties of R2Mn207 pyrochlore rare-earth solid solutions. Physical Review B. Volume 82, Issue 13. 132407/1-4. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.82.132407, which has been published in final for...

This ex situ electrochemical study investigates how the oxygen reduction reaction (ORR) on Bi-doped Ca2Ru2O7 pyrochlore catalysts is affected by the addition of carbonate to the aqueous KOH (1 mol dm ) electrolyte. The parent Ca2Ru2O7 catalyst has been previously reported to be selective towards the generation of CO3 2– on the reaction of O2 with CO2 (in the presence of H2O) at the cathode of l...

We apply the contractor renormalization (CORE) method to the spin half Heisenberg antiferromagnet on the frustrated checkerboard and pyrochlore lattices. Their ground states are spin-gapped singlets which break lattice symmetry. Their effective Hamiltonians describe fluctuations of orthogonal singlet pairs on tetrahedral blocks, at an emergent low energy scale. We discuss low temperature thermo...

Quantum melting of spin ice is proposed for pyrochlore-lattice magnets Pr2TM2O7 (TM=Ir, Zr, and Sn). The quantum superexchange Hamiltonian having a nontrivial magnetic anisotropy is derived on the basis of atomic non-Kramers magnetic doublets. The ground states exhibit a cooperative ferroquadrupole and pseudospin chirality, forming a magnetic analog of smectic liquid crystals. Our theory accoun...