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Engineering two-dimensional superconductivity and Rashba spin-orbit coupling in LaAlO₃/SrTiO₃ quantum wells by selective orbital occupancy.

Herranz G, Singh G, Bergeal N, Jouan A, Lesueur J, Gázquez J, Varela M, Scigaj M, Dix N, Sánchez F, Fontcuberta J - Nat Commun (2015)

Bottom Line: The discovery of two-dimensional electron gases (2DEGs) at oxide interfaces-involving electrons in narrow d-bands-has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons.There is a growing consensus that emerging properties at these novel quantum wells-such as 2D superconductivity and magnetism-are intimately connected to specific orbital symmetries in the 2DEG sub-band structure.Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at LaAlO3/SrTiO3 interfaces.

View Article: PubMed Central - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain.

ABSTRACT
The discovery of two-dimensional electron gases (2DEGs) at oxide interfaces-involving electrons in narrow d-bands-has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons. There is a growing consensus that emerging properties at these novel quantum wells-such as 2D superconductivity and magnetism-are intimately connected to specific orbital symmetries in the 2DEG sub-band structure. Here we show that crystal orientation allows selective orbital occupancy, disclosing unprecedented ways to tailor the 2DEG properties. By carrying out electrostatic gating experiments in LaAlO3/SrTiO3 wells of different crystal orientations, we show that the spatial extension and anisotropy of the 2D superconductivity and the Rashba spin-orbit field can be largely modulated by controlling the 2DEG sub-band filling. Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at LaAlO3/SrTiO3 interfaces.

No MeSH data available.


Related in: MedlinePlus

Anisotropy of the 2D superconductivity at the (001) and (110) interfaces.Sheet resistance of (a) the (110)-interface with t=14 MLs and (b) the (001)-interface with t=10 MLs, under magnetic fields applied parallel to the interface. The field values are indicated in the panels. Panel (c) shows the temperature dependence of out-of-plane μ0Hc2,⊥ and in-plane μ0Hc2,‖ critical fields of (001)—red circles—and (110)—blue triangles—interfaces, corroborating the 2D character of the superconductivity for both orientations. (d) The upper critical fields are displayed as a function of the temperature for both the orientations (field in-plane). The dotted and dashed straight lines indicate the Pauli-limited critical fields . The observation of higher critical fields for the (001) interface is consistent with the larger anisotropy of the 2DEG superconductivity and stronger spatial confinement for (001).
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f2: Anisotropy of the 2D superconductivity at the (001) and (110) interfaces.Sheet resistance of (a) the (110)-interface with t=14 MLs and (b) the (001)-interface with t=10 MLs, under magnetic fields applied parallel to the interface. The field values are indicated in the panels. Panel (c) shows the temperature dependence of out-of-plane μ0Hc2,⊥ and in-plane μ0Hc2,‖ critical fields of (001)—red circles—and (110)—blue triangles—interfaces, corroborating the 2D character of the superconductivity for both orientations. (d) The upper critical fields are displayed as a function of the temperature for both the orientations (field in-plane). The dotted and dashed straight lines indicate the Pauli-limited critical fields . The observation of higher critical fields for the (001) interface is consistent with the larger anisotropy of the 2DEG superconductivity and stronger spatial confinement for (001).

Mentions: We discuss first the implications of band reconstruction on the 2DEG superconductivity. In line with previous reports on (001) (refs 14, 15, 19), we show that the (110)-interface is also superconductive and has a 2D character. Yet, we uncover that the anisotropy of the 2D superconductive state is considerably larger for (001) than for (110). Such a conclusion is readily apparent from the sheet resistance curves measured under the magnetic fields applied in-plane (Fig. 2a,b). It is known that as the 2D limit is approached, increasingly higher in-plane fields are required to suppress the superconductivity, since vortex entry is impeded by the low dimensionality13. Therefore, higher in-plane critical fields imply stronger anisotropy. Inspection of Fig. 2a,b shows that the (001) interface requires much higher in-plane fields (μ0Hc2,‖≈2,200 mT) than the (110) interface (μ0Hc2,‖≈1,000 mT) to induce the transition to the normal state. We conclude, thus, that the 2D anisotropy is larger for (001) than for (110), anticipating a smaller spatial extension of the quantum well along (001).


Engineering two-dimensional superconductivity and Rashba spin-orbit coupling in LaAlO₃/SrTiO₃ quantum wells by selective orbital occupancy.

Herranz G, Singh G, Bergeal N, Jouan A, Lesueur J, Gázquez J, Varela M, Scigaj M, Dix N, Sánchez F, Fontcuberta J - Nat Commun (2015)

Anisotropy of the 2D superconductivity at the (001) and (110) interfaces.Sheet resistance of (a) the (110)-interface with t=14 MLs and (b) the (001)-interface with t=10 MLs, under magnetic fields applied parallel to the interface. The field values are indicated in the panels. Panel (c) shows the temperature dependence of out-of-plane μ0Hc2,⊥ and in-plane μ0Hc2,‖ critical fields of (001)—red circles—and (110)—blue triangles—interfaces, corroborating the 2D character of the superconductivity for both orientations. (d) The upper critical fields are displayed as a function of the temperature for both the orientations (field in-plane). The dotted and dashed straight lines indicate the Pauli-limited critical fields . The observation of higher critical fields for the (001) interface is consistent with the larger anisotropy of the 2DEG superconductivity and stronger spatial confinement for (001).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308716&req=5

f2: Anisotropy of the 2D superconductivity at the (001) and (110) interfaces.Sheet resistance of (a) the (110)-interface with t=14 MLs and (b) the (001)-interface with t=10 MLs, under magnetic fields applied parallel to the interface. The field values are indicated in the panels. Panel (c) shows the temperature dependence of out-of-plane μ0Hc2,⊥ and in-plane μ0Hc2,‖ critical fields of (001)—red circles—and (110)—blue triangles—interfaces, corroborating the 2D character of the superconductivity for both orientations. (d) The upper critical fields are displayed as a function of the temperature for both the orientations (field in-plane). The dotted and dashed straight lines indicate the Pauli-limited critical fields . The observation of higher critical fields for the (001) interface is consistent with the larger anisotropy of the 2DEG superconductivity and stronger spatial confinement for (001).
Mentions: We discuss first the implications of band reconstruction on the 2DEG superconductivity. In line with previous reports on (001) (refs 14, 15, 19), we show that the (110)-interface is also superconductive and has a 2D character. Yet, we uncover that the anisotropy of the 2D superconductive state is considerably larger for (001) than for (110). Such a conclusion is readily apparent from the sheet resistance curves measured under the magnetic fields applied in-plane (Fig. 2a,b). It is known that as the 2D limit is approached, increasingly higher in-plane fields are required to suppress the superconductivity, since vortex entry is impeded by the low dimensionality13. Therefore, higher in-plane critical fields imply stronger anisotropy. Inspection of Fig. 2a,b shows that the (001) interface requires much higher in-plane fields (μ0Hc2,‖≈2,200 mT) than the (110) interface (μ0Hc2,‖≈1,000 mT) to induce the transition to the normal state. We conclude, thus, that the 2D anisotropy is larger for (001) than for (110), anticipating a smaller spatial extension of the quantum well along (001).

Bottom Line: The discovery of two-dimensional electron gases (2DEGs) at oxide interfaces-involving electrons in narrow d-bands-has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons.There is a growing consensus that emerging properties at these novel quantum wells-such as 2D superconductivity and magnetism-are intimately connected to specific orbital symmetries in the 2DEG sub-band structure.Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at LaAlO3/SrTiO3 interfaces.

View Article: PubMed Central - PubMed

Affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193 Bellaterra, Catalonia, Spain.

ABSTRACT
The discovery of two-dimensional electron gases (2DEGs) at oxide interfaces-involving electrons in narrow d-bands-has broken new ground, enabling the access to correlated states that are unreachable in conventional semiconductors based on s- and p- electrons. There is a growing consensus that emerging properties at these novel quantum wells-such as 2D superconductivity and magnetism-are intimately connected to specific orbital symmetries in the 2DEG sub-band structure. Here we show that crystal orientation allows selective orbital occupancy, disclosing unprecedented ways to tailor the 2DEG properties. By carrying out electrostatic gating experiments in LaAlO3/SrTiO3 wells of different crystal orientations, we show that the spatial extension and anisotropy of the 2D superconductivity and the Rashba spin-orbit field can be largely modulated by controlling the 2DEG sub-band filling. Such an orientational tuning expands the possibilities for electronic engineering of 2DEGs at LaAlO3/SrTiO3 interfaces.

No MeSH data available.


Related in: MedlinePlus