|일시||May. 13 (Fri.), 02:30 PM|
|연사||Dr. Kun-Rok Jeon(Department of Physics, Chung-Ang University)|
“Topological Superconducting Spintronics Towards Zero-Power Computing Technologies”
Dr. Kun-Rok Jeon
Department of Physics, Chung-Ang University
May. 13 (Fri.), 02:30 PM
Semiconductor (SC) spintronics [1-4] aims to integrate memory and logic functions into a single device. Ferromagnetic tunnel contacts have emerged as a robust and technically viable method to inject spin current into a SC up to room temperature, and to detect it [3-7]. Intriguingly, it has been established that the spin current in ferromagnetic tunnel contacts can be created by thermal means (driven by a heat flow), namely Seebeck spin tunneling . So far, the creation of thermal spin current relies on the spin-dependent energy dispersion of electronic states around the Fermi energy (EF), which determines thermoelectric properties. In the first part of my talk, I will describe a conceptually new approach to tailor the thermal spin current in ferromagnetic tunnel contacts to SCs exploiting spin-dependent thermoelectric properties away from EF through the application of a bias voltage across the tunnel contact [9,10].
Combining superconductivity with spintronics brings in a variety of notable phenomena which do not exist in the normal state, for instance quantum coherence, superconducting exchange coupling and spin-polarized triplet supercurrents [11,12]. This nascent field of superconducting spintronics promises to realize zero-energy-dissipation spin transfer and magnetization switching. Recent equilibrium (zero-bias) studies of the Josephson effect in S/FM/S (FM: ferromagnet; S: Superconductor) junctions and the critical temperature Tc modulation in FM/S/FM and S/FM/FM' superconducting spin valves have demonstrated that engineered magnetically-inhomogeneous S/FM interfaces can generate long-range triplet pairing states which explicitly carry spin [11,12]. However, direct measurement of triplet spin transport through a singlet S has not so far been achieved. In the second part, I will describe an essentially different approach, namely, a time-dependent ferromagnetic magnetization [ferromagnetic resonance (FMR)] can drive spin-polarized transport in a singlet S via spin-triplet states induced by spin-orbit coupling [13,14].
If time permits, I will briefly outline outstanding technical issues for the realization of energy-efficient (or even dissipation-less) spintronic technologies and present my research direction of how to address these issues via topology physics [15,16].
Reference:  Rev. Mod. Phys. 80, 1517 (2008),  Rev. Mod. Phys. 76, 323 (2004),  Nat. Mater. 11, 400 (2012),  Semicond. Sci. Technol. 27, 083001 (2012),  Nature 462, 491 (2009),  Appl. Phys. Express 4, 023003 (2011),  Phys. Rev. Appl. 2, 034005 (2014),  Nature 475, 82 (2011),  Nat. Mater. 13, 360 (2014),  Phys. Rev. B 91, 155305 (2015),  Nat. Phys. 11, 307 (2015),  Rep. Prog. Phys. 78, 104501 (2015),  Nat. Mater. 17, 499 (2018),  Phys. Rev. X 10, 031020 (2020),  Nat. Mater. 20, 1358 (2021),  Under review in Nat. Nanotech. (2022).
Contact: SunYoung Choi, (firstname.lastname@example.org)
Center for Quantum Coherence in Condensed Matter, KAIST