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|Title:||Carrier concentration-tuned phase transitions in high-Tc cuprates and perovskite oxide interfaces||Authors:||ZENG SHENGWEI||Keywords:||cuprate superconductor, oxide interface, field effect, ionic liquid, phase transition, doping||Issue Date:||20-Aug-2014||Citation:||ZENG SHENGWEI (2014-08-20). Carrier concentration-tuned phase transitions in high-Tc cuprates and perovskite oxide interfaces. ScholarBank@NUS Repository.||Abstract:||We investigated the modulation of charge carriers and the resultant phase transitions in high-Tc cuprate and oxide interface by chemical and electric field effect doping. Firstly, by doping La and modifying the oxygen composition in YBa2Cu3Oy system, we obtained an ambipolar cuprate in which both electrons and holes can be doped in a single parent insulator. Secondly, using ionic liquid-assisted electric field effect, the carrier density in an electron-doped cuprate Pr2-xCexCuO4 was quasi-continuously tuned and a two-dimensional superconductor-insulator transition (SIT) was realized. The SIT occurs at a critical sheet resistance much lower than pair quantum resistance RQ=h/(2e)2=6.45 k Ohms, suggesting the formation of fermionic excitations at the insulating phase in electron-doped cuprate. Finally, ionic liquid-assisted field effect was also performed on LaAlO3/SrTiO3 interface. Reversible metallic-insulating phase transition, field-effect transistor operation and quantum oscillations of the conductance were observed in liquid-gated LaAlO3/SrTiO3 interface.||URI:||http://scholarbank.nus.edu.sg/handle/10635/118276|
|Appears in Collections:||Ph.D Theses (Open)|
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