Unconventional Quantum Oscillations in EuO/KTaO₃ Heterointerface

The coexistence of electric-field controlled superconductivity and spin-orbit interaction in two-dimensional electron gas (2DEG) based on complex oxides (e.g., SrTiO₃ and KTaO₃) hold great promise for advancement in spintronics and quantum computing. However, a comprehensive understanding of the electronic bands that give rise to the multifunctional character of these 2DEGs remains elusive. To address this, we recently investigated quantum oscillations in the magnetoresistance of a KTaO₃-2DEG in high magnetic fields (60 T).<br/>KTaO₃ is a 5<i>d </i>transition metal oxide, exhibiting a lighter effective mass of electrons and a stronger spin-orbit interaction at its conducting surface/interface than its counterpart SrTiO₃ [1-2]. A high-mobility spin-polarized 2DEG with the superconducting feature is discovered at the EuO/KTaO₃ interface [3]. In this talk, I will present novel insights into the electronic states of the EuO/KTaO₃ interface investigated through Shubnikov-de Haas (SdH) oscillations. Remarkably, we observed a progressive increase in cyclotron mass and oscillation frequency with the magnetic field, indicating the presence of non-trivial electronic bands [4]. Besides providing experimental evidence for topological-like electronic states in KTaO₃-2DEG, these results shed light on the recent predictions of topological states in the 2DEG based on similar perovskite transition metal oxides.<br/><b>References</b><br/>[1] K. Rubi <i>et al</i>., npj Quantum Materials <b>5</b>, 1 (2020), King, P. D. C. <i>et al</i>. Phys. Rev. Lett. <b>108</b>, 117602 (2012).<br/>[2] K. Rubi <i>et al</i>., Phy. Rev. Research <b>3</b>, 033234 (2021).<br/>[3] H. Zhang <i>et al</i>., Phys. Rev. Lett. <b>121</b>, 116803 (2018), Liu <i>et al</i>., Science <b>371</b>, 716 (2021).<br/>[4] K. Rubi <i>et al</i>., arXiv:2307.04854 (2023).<br/><br/><b>Acknowledgement:</b> We acknowledge support from the National High Magnetic Field Laboratory, supported by the National Science Foundation through NSF/DMR-1644779 and the State of Florida, and the US Department of Energy "Science of 100 Tesla" BES program.