Novel low dimensional quantum phenomena are expected at (110) LaAlO 3 /SrTiO 3 (LAO/STO) interfaces after the quasi two dimensional electron gas similar to that of (001) LAO/STO interfaces was found [G. Herranz et al., Sci. Rep. 2, 758 (2012) and A. Annadi et al., Nat. Commun. 4, 1838]. Here, two dimensional superconductivity of (110) LAO/STO samples with a superconducting transition temperature of 184 mK is demonstrated based on systematical transport measurements. The two dimensional characteristic of the superconductivity is confirmed by analyzing the Berezinskii-Kosterlitz-Thouless transition. The estimated superconductive thickness is about 18 nm. These features of superconductivity of (110) LAO/STO interfaces are comparable to those of (001) LAO/STO interfaces. This discovery may inspire a new round of upsurge on study of LAO/STO interfaces.

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Experimentally, we found the percentage of low valence cations, the ionization energy of cations in film, and the band gap of substrates to be decisive for the formation of two-dimensional electron gas at the interface of amorphous/crystalline oxide (a-2DEG). Considering these findings, we inferred that the charge transfer from the film to the interface should be the main mechanism of a-2DEG formation. This charge transfer is induced by oxygen defects in film and can be eliminated by the electron-absorbing process of cations in the film. Based on this, we propose a simple dipole model that successfully explains the origin of a-2DEG, our experimental findings, and some important properties of a-2DEG.

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A systematic study of the two-dimensional electron gas at LaAlO 3 /SrTiO 3 (110) interface reveals an anisotropy along two specific directions, [001] and 1 10 . The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the 1 10 direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin-orbit coupling, and the spin relaxation mechanism along both directions belongs to D'yakonov-Perel' (DP) scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the 1 10 direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions.