Complex oxides show a rich variety of functionalities through their strong coupling to the lattice, electron, orbital, and spin degrees of freedom not only at oxide heterointerfaces but also in layered cuprates. For the topic of oxide heterointerfaces, with advances in growth, delicate tuning of the atomic termination at the interface with layer-by-layer precision is now achievable. The improvements in growth open up opportunities to manipulate the coupling of 3d electrons at complex oxide interfaces, creating intriguing phenomena that are not attainable in bulk constituents alone. For example, two-dimensional electron gases have been found at LaAlO3/SrTiO3 heterointerfaces. For the topic of high-temperature layered cuprates (for example, YBa2Cu3O6+x (YBCO6+x)), charge order (CO) has been the key to understanding the full picture for high transition temperature superconductors. However, two central questions that involve the general picture of the stacking pattern for the CO interlayer in YBCO6+x and how exactly the CuO chain influences the CO on the CuO2 plane remain an open issue. Investigating the nanostructure of the CO and its spatial interplay with superconductivity, as well as the relation between CuO2 bilayers and CuO chain layers simultaneously with atomic-scale spatial and energy resolution, is still under debate. Disentangling the physical origins of the interface properties and interlayer electronic states in complex oxides requires an experimentally direct probe localized at the interfaces and characterization of atomically resolved electronic states in oxides. In this paper, we review the utilization of cross-sectional scanning tunneling microscopy (XSTM) and spectroscopy (XSTS) to directly probe electronic states with atomic precision right at and across complex oxide interfaces and interlayers. With this technique, we probe the structural and electronic properties in complex oxides, revealing the underlying detailed electronic structure (e.g., local electronic density of states and ferroelectric polarization in oxide interfaces, as well as the spatial configuration of CO and its interplay with the superconductivity in YBCO6+x). This forms the basis for an atomic-scale physical understanding of complex oxides, which is also central for designing complex oxide devices.
- Atomically resolved interlayer electronic states in complex oxides by using cross-sectional scanning tunneling microscopy
- Bo-Chao Huang - Natl Taiwan Univ, Dept Phys, Taipei 106, TaiwanChun-Chih Hsu - National Taiwan UniversityYing-Hao Chu - National Tsing Hua University, College of Semiconductor ResearchYa-Ping Chiu - University of Taipei
- Elsevier
- 12
- MOST 109-2923-M-002-009-MY3; 57447615 / German Academic Exchange Service MOST-DAAD Project-Based Personnel Exchange Program MOST 109-2628-M-002-005-MY3; MOST 110-2119-M-002-015-MBK; MOST 110-2622-8-002-014 / Ministry of Science and Technology (MOST) of Taiwan; National Science & Technology Council (NSTC) Taiwan 111L900802 / Center of Atomic Initiative for New Materials, National Taiwan Univ., Taipei, Taiwan from the Featured Areas Research Center Program Ministry of Science and Technology (MOST); Ministry of Science and Technology, China AS-IA-107-M03 / Academia Sinica; Academia Sinica - Taiwan NTU-110L7839; NTU-111L7722 / National Taiwan Univ.
- Journal article
- 01/05/2022
- Progress in surface science, Vol.97(2), 100662
- English