Strain-Charge Entanglement in LaAlO₃/SrTiO₃ Heterostructure
P. W. Lee1,2*, M.-W. Chu1, V. N. Singh2,3, G. Y. Guo2,4, C. H. Chen1, H.-J. Liu5, J.-C. Lin5, Y.-H. Chu5
1Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
4Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan
5Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan
* presenting author:Pei-Wei Lee,
The conductive heterointerface of LaAlO₃/SrTiO₃ displays a plethora of unexpected physical phenomena, ranging from two-dimensional superconductivity, interfacial ferromagnetism, to sensitivity to electromechanical stimuli like insulating ferroelectrics. The metallic interface is typically depicted by polar catastrophe, while this model remains contested up to the date let alone its controversy in tackling the superconducting and ferromagnetic properties. Here, we resolve this long-standing puzzle using atomically-resolved electron energy-loss spectroscopy, firmly pinpointing the respective roles of chemical, electronic, and structural parameters at play. The interfacial conductivity was readily found to be the direct result of an intriguing strain-accommodation mechanism at the interface, shedding new light on the various collective properties of this novel interface.

Keywords: LaAlO3/SrTiO3 (LAO/STO), two-dimensional electron gas (2DEG), conductive interface, heterostructure, strain