Side Gate Tunable Josephson Junctions at the LaAlO₃/SrTiO₃ Interface

Abstract

Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate-tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale. We demonstrate that the side gates enable reliable tuning of both the normal-state resistance and the critical (Josephson) current of the constrictions. The conductance and Josephson current show mesoscopic fluctuations as a function of the applied side gate voltage, and the analysis of their amplitude enables the extraction of the phase coherence and thermal lengths. Finally, we realize a superconducting quantum interference device in which the critical currents of each of the constriction-type Josephson junctions can be controlled independently via the side gates.

Quantum paraelectricity probed by superconducting resonators

“…The narrow 10-μm gap converts a relatively small voltage to an intense and localized average electric field (1 V ≈ 100 kV/m) whose magnitude is further enhanced in the proximity of the CPW by the inhomogeneous density of electric-field lines (see Supplemental Material S2 [20]). A similar local gating scheme was used recently in transport experiments in oxide systems [22][23][24]. The modification of the local dielectric constant caused by the dc bias results in a change of the total capacitance of the resonator and a corresponding shift of its resonance frequencies.…”

Nanoscale patterning of electronic devices at the amorphous LaAlO3/SrTiO3 oxide interface using an electron sensitive polymer mask

“…Alternatively, to avoid possible damage due to processing on the samples after the growth of the toplayer, either metallic gates can be used as a part of the mask structure 17 or nearby regions of the 2DES itself can be utilized for gating. 20,26 Figure 4 demonstrates the latter approach using the PMMA as the patterning mask for defining a 500 nm wide channel with nearby 2DES side-gates as shown in Fig. 1(a).…”

“…1(a). 26 The separation between the gates and the channel was likewise 500 nm. The conductance of the devices as a function of the voltage V SG applied to the side-gates and back-gate is shown in Figs. 4(b)-4(d) for a temperature of 20 mK.…”

“…For all three gates, the conductance significantly decreases with lowering gate potential as the channel is depleted of carriers and the effect of the two side gates is remarkably symmetric. The gate-efficiency, however, progressively decreases at lower gate voltage due to the field dependent dielectric constant of STO, 26 and the side-gates could be operated without leakage only within the range of [À0.15 V,1 V]. A similar device with lower dimensionality was fabricated after these measurements.…”

Self‐Assembly of Perovskite Crystals Anchored Al2O3‐La2O3 Nanofibrous Membranes with Robust Flexibility and Luminescence

“…Owing to its stable physical and chemical properties, lanthanum aluminate has intensive applications as substrates for magnetic thin films, superconductors, and luminescent host materials . Hence, we selected the flexible Al 2 O 3 ‐La 2 O 3 nanofibrous membranes as substrate.…”