Giant Tunability of Rashba Splitting at Cation-Exchanged Polar Oxide Interfaces by Selective Orbital Hybridization

Hao Xu; Hang Li; Nicolas Gauquelin; Xuejiao Chen; Wen-Feng Wu; Yuchen Zhao; Liang Si; Di Tian; Lei Li; Yulin Gan; Shaojin Qi; Minghang Li; Fengxia Hu; Jirong Sun; Daen Jannis; Pu Yu; Gang Chen; Zhicheng Zhong; Milan Radovic; Johan Verbeeck; Yunzhong Chen; Baogen Shen

doi:10.1002/adma.202313297

Giant Tunability of Rashba Splitting at Cation-Exchanged Polar Oxide Interfaces by Selective Orbital Hybridization

Adv Mater. 2024 Mar 12:e2313297. doi: 10.1002/adma.202313297. Online ahead of print.

Authors

Hao Xu^{1

2}, Hang Li³, Nicolas Gauquelin⁴, Xuejiao Chen⁵, Wen-Feng Wu^{6

7}, Yuchen Zhao^{1

2}, Liang Si⁸, Di Tian⁹, Lei Li¹⁰, Yulin Gan^{1

2}, Shaojin Qi^{1

2}, Minghang Li^{1

2}, Fengxia Hu^{1

2}, Jirong Sun^{1

2}, Daen Jannis⁴, Pu Yu⁹, Gang Chen¹¹, Zhicheng Zhong⁵, Milan Radovic³, Johan Verbeeck⁴, Yunzhong Chen^{1

2}, Baogen Shen^{1

2

5

12}

Affiliations

¹ Beijing National Laboratory of 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.
³ Photon Science Division, Paul Scherrer Institute, Villigen, 5232, Switzerland.
⁴ Electron Microscopy for Materials Science (EMAT), University of Antwerp, 4Groenenborgerlaan 171, Antwerp, 2020, Belgium.
⁵ CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China.
⁶ Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, P. R. China.
⁷ Science Island Branch of Graduate School, University of Science and Technology of China, Hefei, 230026, P. R. China.
⁸ School of Physics, Northwest University, Xi'an, 710127, China.
⁹ State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China.
¹⁰ Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE) and Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, 127 West Youyi Road, Xi'an, 710072, China.
¹¹ Department of Physics and HKU-UCAS Joint Institute for Theoretical and Computational Physics at Hong Kong, The University of Hong Kong, Hong Kong, 999077, China.
¹² Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou, Jiangxi, 341000, China.

PMID: 38475975
DOI: 10.1002/adma.202313297

Abstract

The 2D electron gas (2DEG) at oxide interfaces exhibits extraordinary properties, such as 2D superconductivity and ferromagnetism, coupled to strongly correlated electrons in narrow d-bands. In particular, 2DEGs in KTaO₃ (KTO) with 5d t_2g orbitals exhibit larger atomic spin-orbit coupling and crystal-facet-dependent superconductivity absent for 3d 2DEGs in SrTiO₃ (STO). Herein, by tracing the interfacial chemistry, weak anti-localization magneto-transport behavior, and electronic structures of (001), (110), and (111) KTO 2DEGs, unambiguously cation exchange across KTO interfaces is discovered. Therefore, the origin of the 2DEGs at KTO-based interfaces is dramatically different from the electronic reconstruction observed at STO interfaces. More importantly, as the interface polarization grows with the higher order planes in the KTO case, the Rashba spin splitting becomes maximal for the superconducting (111) interfaces approximately twice that of the (001) interface. The larger Rashba spin splitting couples strongly to the asymmetric chiral texture of the orbital angular moment, and results mainly from the enhanced inter-orbital hopping of the t_2g bands and more localized wave functions. This finding has profound implications for the search for topological superconductors, as well as the realization of efficient spin-charge interconversion for low-power spin-orbitronics based on (110) and (111) KTO interfaces.

Keywords: Rashba spin‐orbit coupling; conducting oxide interfaces; magnetoresistance; spintronics.

Abstract

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