Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices.
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Here, we report on the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage.We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition.Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates.
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Affiliation: Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France.
ABSTRACT
The recent development in the fabrication of artificial oxide heterostructures opens new avenues in the field of quantum materials by enabling the manipulation of the charge, spin and orbital degrees of freedom. In this context, the discovery of two-dimensional electron gases (2-DEGs) at LaAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage. We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition. Magneto-transport measurements show that the Rashba coupling constant increases linearly with the interfacial electric field. Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates. No MeSH data available. Related in: MedlinePlus |
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Mentions: After the sample was cooled, the top-gate voltage VTG was first increased to +110 V, beyond the saturation threshold of the resistance. During this operation, electrons are added in the quantum well, increasing the Fermi energy to its maximum value (i.e., the top of the well)19. In comparison with back-gate experiments where the relationship between the carrier density (n) and the back-gate voltage VBG is not trivial owing to the electric-field-dependent dielectric constant of SrTiO313, here, the carrier density is expected to increase linearly with VTG. Figure 2 shows the sheet carrier density , extracted from the Hall effect measurements performed up to B = 4 T as a function of the top-gate voltage VTG, for two different back-gate voltages (VBG = 0 V and VBG = −15 V). For VBG = 0 V, the linear increase in n is observed with VTG only for negative VTG. The non-physical decrease in n with VTG for positive gate voltages is caused by the incorrect determination of the carrier density at low magnetic fields. It was shown that at the LaAlO3/SrTiO3 interface, the Hall voltage is no longer linear with the magnetic field for strong filling of the quantum well because of multi-band transport122021. To reach a doping regime where the one-band approximation is valid, a negative back-gate VBG = −15 V was applied producing a depletion of the highest energy sub-bands that accommodate the highly-mobile carriers, responsible of the decrease of the Hall number at positive VTG. Figure 2 shows that in this case, the linear dependence of with VTG can be recovered. The linear fit of slope is obtained from numerical simulations of the electric field-effect by a finite elements method assuming a dielectric constant for the Si3N4 layer (see the inset in Fig. 2). Finally, the following relationship between the carrier density and top-gate voltage is deduced: n = 5.0 × 1010VTG + 1.69 × 1013 e- .cm-2. |
View Article: PubMed Central - PubMed
Affiliation: Laboratoire de Physique et d'Etude des Matériaux -CNRS-ESPCI ParisTech-UPMC, PSL Research University, 10 Rue Vauquelin, 75005 Paris, France.
No MeSH data available.