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Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices.

Hurand S, Jouan A, Feuillet-Palma C, Singh G, Biscaras J, Lesne E, Reyren N, Barthélémy A, Bibes M, Villegas JE, Ulysse C, Lafosse X, Pannetier-Lecoeur M, Caprara S, Grilli M, Lesueur J, Bergeal N - Sci Rep (2015)

Bottom Line: 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.

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.

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

Field-effect control of the superconductivity.(a) Sheet resistance of the device as a function of temperature for different VTG. (b) Sheet resistance normalised by its value at T = 350 mK plotted with a colour scale as a function of temperature (left axis) and top-gate voltage. The carrier densities corresponding to the top-gate voltages have been added in the top axis. The sheet resistance at T = 350 mK is plotted as a function of top-gate voltage on the right axis. The critical temperature Tc is plotted as function of the top-gate voltage on the left axis for the different criteria: drop of 10%, 50% and 90% of the normal resistance taken at T = 350 mK.
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f3: Field-effect control of the superconductivity.(a) Sheet resistance of the device as a function of temperature for different VTG. (b) Sheet resistance normalised by its value at T = 350 mK plotted with a colour scale as a function of temperature (left axis) and top-gate voltage. The carrier densities corresponding to the top-gate voltages have been added in the top axis. The sheet resistance at T = 350 mK is plotted as a function of top-gate voltage on the right axis. The critical temperature Tc is plotted as function of the top-gate voltage on the left axis for the different criteria: drop of 10%, 50% and 90% of the normal resistance taken at T = 350 mK.

Mentions: In the following, the back gate voltage VBG was always set to 0 V unless otherwise stated. Figure 3a shows the sheet resistance of the device as a function of temperature measured for different top-gate voltages in the range [−110 V, +110 V], where the leakage gate current is negligible (<0.1 nA). The variation in VTG induces a modulation in the normal state resistance by two orders of magnitude. Figure 3b summarises the variations of the normalised resistance R/R(T = 350 mK) as a function of temperature (T) and top-gate voltage VTG on a phase diagram. The corresponding n is also indicated on the top axis. The device displays a gate-dependent superconducting transition, whose critical temperature Tc describes a partial dome as a function of VTG, similar to that observed with a back-gate111214. The maximum Tc, corresponding to optimal doping, is around 250 mK. In the underdoped region, a decrease in the gate voltage causes Tc to continuously decrease from its maximum value to zero. A superconductor-to-insulator quantum phase transition takes place around VTG = −90 V. The critical sheet resistance at the transition is , which is close to the quantum of resistance of bosons with 2e charges, . For large negative voltages, corresponding to low electron densities, the sheet resistance increases strongly when approaching the insulating state. In the overdoped region, the addition of electrons into the quantum well with the top-gate produces a small decrease in Tc whose origin is currently under debate. Such behaviour has also been observed in doped bulk SrTiO322 and could be reinforced by the two-dimensionality of the interface23. The current-voltage characteristics of the device for different top-gate voltages are shown in Supplementary Material.


Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices.

Hurand S, Jouan A, Feuillet-Palma C, Singh G, Biscaras J, Lesne E, Reyren N, Barthélémy A, Bibes M, Villegas JE, Ulysse C, Lafosse X, Pannetier-Lecoeur M, Caprara S, Grilli M, Lesueur J, Bergeal N - Sci Rep (2015)

Field-effect control of the superconductivity.(a) Sheet resistance of the device as a function of temperature for different VTG. (b) Sheet resistance normalised by its value at T = 350 mK plotted with a colour scale as a function of temperature (left axis) and top-gate voltage. The carrier densities corresponding to the top-gate voltages have been added in the top axis. The sheet resistance at T = 350 mK is plotted as a function of top-gate voltage on the right axis. The critical temperature Tc is plotted as function of the top-gate voltage on the left axis for the different criteria: drop of 10%, 50% and 90% of the normal resistance taken at T = 350 mK.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525493&req=5

f3: Field-effect control of the superconductivity.(a) Sheet resistance of the device as a function of temperature for different VTG. (b) Sheet resistance normalised by its value at T = 350 mK plotted with a colour scale as a function of temperature (left axis) and top-gate voltage. The carrier densities corresponding to the top-gate voltages have been added in the top axis. The sheet resistance at T = 350 mK is plotted as a function of top-gate voltage on the right axis. The critical temperature Tc is plotted as function of the top-gate voltage on the left axis for the different criteria: drop of 10%, 50% and 90% of the normal resistance taken at T = 350 mK.
Mentions: In the following, the back gate voltage VBG was always set to 0 V unless otherwise stated. Figure 3a shows the sheet resistance of the device as a function of temperature measured for different top-gate voltages in the range [−110 V, +110 V], where the leakage gate current is negligible (<0.1 nA). The variation in VTG induces a modulation in the normal state resistance by two orders of magnitude. Figure 3b summarises the variations of the normalised resistance R/R(T = 350 mK) as a function of temperature (T) and top-gate voltage VTG on a phase diagram. The corresponding n is also indicated on the top axis. The device displays a gate-dependent superconducting transition, whose critical temperature Tc describes a partial dome as a function of VTG, similar to that observed with a back-gate111214. The maximum Tc, corresponding to optimal doping, is around 250 mK. In the underdoped region, a decrease in the gate voltage causes Tc to continuously decrease from its maximum value to zero. A superconductor-to-insulator quantum phase transition takes place around VTG = −90 V. The critical sheet resistance at the transition is , which is close to the quantum of resistance of bosons with 2e charges, . For large negative voltages, corresponding to low electron densities, the sheet resistance increases strongly when approaching the insulating state. In the overdoped region, the addition of electrons into the quantum well with the top-gate produces a small decrease in Tc whose origin is currently under debate. Such behaviour has also been observed in doped bulk SrTiO322 and could be reinforced by the two-dimensionality of the interface23. The current-voltage characteristics of the device for different top-gate voltages are shown in Supplementary Material.

Bottom Line: 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.

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.

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