Abstract
We report that the surface conductivity of Na2IrO3 crystal is extremely tunable by high energy Ar plasma etching and can be tuned from insulating to metallic with increasing etching time. Temperature dependent electrical transport for the metallic samples show signatures of first order phase transitions which are consistent with charge or spin density wave like phase transitions predicted recently. Additionally, grazing-incidence small-angle x-ray scattering (GISAXS) reveal that the room temperature surface structure of Na2IrO3 does not change after plasma etching.
Highlights
5d transition metal oxides (TMO) are candidates for novel magnetism.[1,2] In 3d TMOs, electron correlation (U) is the most significant energy scale
We find anomalies in the electrical transport properties which are consistent with spin/charge density wave-like phase transitions or structural transitions in these surface doped Na2IrO3 crystals
Since the thickness of the surface layer modified by the Reactive-ion etching (RIE) is unknown and probably depends on the exposure time of plasma etching, D estimated above can be used as a lower limit
Summary
5d transition metal oxides (TMO) are candidates for novel magnetism.[1,2] In 3d TMOs, electron correlation (U) is the most significant energy scale. Iridates A2IrO3 (A = Na, Li) have been recognized as spin-orbit assisted Jeff = 1/2 Mott insulators.[1,8,9,10] The magnetic frustration observed in these materials is argued to arise from the presence of dominant bond-directional Kitaev-like exchange interactions with additional Heisenberg exchange present.[10,11] Recent predictions have been made of novel states emerging on doping the honeycomb lattice Kitaev-Heisenberg model. Predicted novel states include topological superconductivity,[12,13] spin/charge density waves, electronic dimerization instabilities, and bond order instabilities.[14] This motivated us to explore the properties of doped Na2IrO3 crystals. We find anomalies in the electrical transport properties which are consistent with spin/charge density wave-like phase transitions or structural transitions in these surface doped Na2IrO3 crystals
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