关键词: Cd2Ru2O7烧绿石/
金属-绝缘体转变/
反铁磁有序
English Abstract
Effect of Pb doping on metallic state of cubic pyrochlore Cd2Ru2O7
Jiao Yuan-Yuan1,2,Sun Jian-Ping1,2,
Prashant Shahi1,2,
Liu Zhe-Hong1,2,
Wang Bo-Sen1,2,
Long You-Wen1,2,
Cheng Jin-Guang1,2
1.Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China;
2.School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Fund Project:Project supported by the National Key RD Program of China (Grant No. 2018YFA0305700), the National Basic Research Program of China (Grant No. 2014CB921500), the National Natural Science Foundation of China (Grant No. 11574377), and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences, China (Grant No. QYZDB-SSW-SLH013).Received Date:22 February 2018
Accepted Date:11 April 2018
Published Online:20 June 2019
Abstract:Many exotic phenomena in strongly correlated electron systems, such as unconventional superconductivity, metal-insulator transition, and quantum criticality, take place in the intermediate regime between localized and itinerant electronic state. To understand the electronic behaviors near the localized-to-itinerant crossover remains a challenging problem in condensed matter physics. The Ru5+ cubic pyrochlores A2Ru2O7 (A=Cd, Cd, Hg) constitute such a system that the Ru-4d electrons acquire characters of both itinerancy and localization. In addition, the magnetic Ru5+ ions that are situated on the vertices of corner-shared tetrahedral lattice are expected to experience strong geometrical frustration given an antiferromagnetic (AF) arrangement. In this work, we investigate the cubic pyrochlore Cd2Ru2O7, which develops a peculiar metallic state below the AF transition. We synthesize a series of Pb-doped Cd2-xPbxRu2O7 (0 x 2) polycrystalline samples under high-pressure condition, and study the effects of Pb doping on their crystal structure and physical properties. Although the Pb2Ru2O7 pyrochlore is a Pauli paramagnetic metal, we find that the substitution of 10% Pb2+ for Cd2+ in Cd1.8Pb0.2Ru2O7 converts the metallic state of Cd2Ru2O7 into an insulating ground state, in a manner similar to the consequence of exerting hydrostatic pressure or substituting 10% Ca2+ for Cd2+ ions as we found recently. We propose that the electronic state of Cd2Ru2O7 be located at the itinerancy to localization crossover, and the introduction of chemical disorder via Pb2+ substitution may enhance the localized character and induce the metal-to-insulator transition. Our results further demonstrate that the cubic Ru5+ pyrochlore oxides offer an important paradigm for studying the exotic physics of correlated electrons on the border of (de)localization in the presence of strong geometrical frustration.
Keywords: Cd2Ru2O7 pyrochlore/
metal-insulator transition/
antiferromagnetic order
