Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-pa...Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-particle tunneling in attractive charging energy is usually prohibited by ground states with electrons in pairs. We find a microscopic mechanism to induce single-particle sates from pair states. As a consequence, in the nonpolarized metal terminal a remarkable pure spin current with no charge currents survives over a wide range of gate- and bias- voltages, which is rather crucial for experimental observation and design of spintronic devices. In addition, a significant spin-filter effect is presented in certain bias regime.展开更多
基金This work was supported by the Program for New Century Excellent Talents in University （NCET） of China （Grant No. NCET-10-0090）, the National Natural Science Foundation of China （Grant Nos. 11174088 and 11274124）, the State Key Program for Basic Researches of China （Grant Nos. 2006CB921803 and 2010CB923400）, the Program for Changjiang Scholars and Innovative Research Team in University （PCSIRT） （Grant No. IRT1243）, and the Natural Science Foundation of Guangdong Province of China （Grant No. S2012010010681）.
文摘Single-particle sequential tunneling is studied through a negative-U center hybridized with a superconducting, a ferromagnetic, and a normal metal electrodes. In stark contrast to the case of positive U, the single-particle tunneling in attractive charging energy is usually prohibited by ground states with electrons in pairs. We find a microscopic mechanism to induce single-particle sates from pair states. As a consequence, in the nonpolarized metal terminal a remarkable pure spin current with no charge currents survives over a wide range of gate- and bias- voltages, which is rather crucial for experimental observation and design of spintronic devices. In addition, a significant spin-filter effect is presented in certain bias regime.
