Anisotropic superconductivity and frozen electronic states at the (111) LaAlO3/SrTiO3 interface

Abstract

We report measurements of the superconducting properties of the two-dimensional gas that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) in the (111) crystal orientation, a system that permits in-situ tuning of carrier density and disorder by means of a back gate voltage, Vg. Like the (001) oriented LAO/STO interface, superconductivity at the (111) LAO/STO interface can be tuned by Vg. The 2D superconductivity in these (111) LAO/STO samples shows an in-plane anisotropy, being different along different interface crystal directions, and 'remembers' the disorder landscape at which they are cooled through the superconducting transition. The low energy scale and other characteristics of this memory effect distinguish it from charge-trapping effects previously observed in (001) interface samples.

Magnetic and Nematic Orders of the Two-Dimensional Electron Gas at Oxide (111) Surfaces and Interfaces

“…Recently, various groups have started to probe 2DEGs at oxide (111) surfaces and interfaces, for instance induced by photon [28] or ion [29,30] irradiation at the (111) STO surface, as well as that at the (111) LAO-STO interface [31][32][33][34][35]. Part of this interest stems from proposals for realizing topologically nontrivial phases along this growth direction [36][37][38][39][40][41][42][43].…”

“…Angle resolved photoemission spectroscopy (ARPES) on the (111) STO surface reveals a Fermi surface (FS) composed of all three t 2g orbitals, which appears to preserve the expected hexagonal symmetry [28,29]. However, very recent experiments have discovered, via measurements of magnetotransport [30][31][32][33] and the resistive transition into the SC state [35], that this (111) 2DEG exhibits an anisotropy which sets in at low temperatures, spontaneously breaking the hexagonal symmetry. While a weak resistive anisotropy may arise from the ∼ 100 K pseudo-cubic to pseudo-tetragonal transition of bulk STO [45], the onset temperature seen in these experiments is much lower, T ani ∼ 4-30 K depending on the sample and the electron density.…”

Strong spin-orbit coupling and magnetism in (111) (La0.3Sr0.7)(Al0.65Ta0.35Bal1, Huang2, Han3 et al. 2018Phys. Rev. BSelf Cite4290View full textAdd to dashboardCite

“…21,22 How this complex band structure affects various properties is just beginning to be explored. 23,24 Recent transport experiments on (111) LaAlO 3 /STO (LAO/STO) have shown surprising anisotropies related to the crystalline axes, dependent on an applied V g , 9,[25][26][27][28][29] as well as a non-monotonic dependence of phase coherence time τ φ and spin-orbit scattering time τ so on V g . 30 Here we report studies of the MR of LSAT deposited epitaxially on (111) STO.…”

Anisotropic magnetoresistance in multiband systems: Two-dimensional electron gases and polar metals at oxide interfaces

“…Similarly, an in-plane magnetic field is found to have a significant impact on charge transport, leading to a large negative magnetoresistance in (001) 2DEGs over a range of densities 23,30,31 . More recent experiments have begun to create and probe 2DEGs at oxide (111) surfaces and interfaces [32][33][34][35][36][37][38][39][40][41] which have been proposed to host topological phases [42][43][44][45][46][47][48][49] . Such (111) interfaces typically lead to more tightly confined 2DEGs 50 .…”

“…Such (111) interfaces typically lead to more tightly confined 2DEGs 50 . Transport experiments 22,[35][36][37]39,51 on such 2DEGs have studied the anisotropic magnetoresistance (AMR): the change in the diagonal resistivity when the angle between the current direction and the in-plane magnetic field is varied. AMR has also been studied theoretically in the context of spin-dependent impurity scattering on 2DEG samples with finite magnetization 52,53 and in the context of ferromagnetic semiconductors [54][55][56] A useful analysis of the symmetry constraints on the AMR is presented in Ref.…”