Limits...
Long-range electronic reconstruction to a dxz,yz-dominated Fermi surface below the LaAlO₃/SrTiO₃ interface.

Petrović AP, Paré A, Paudel TR, Lee K, Holmes S, Barnes CH, David A, Wu T, Tsymbal EY, Panagopoulos C - Sci Rep (2014)

Bottom Line: However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear.Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO₃ emerge simultaneously at higher n(2D).We distinguish three areas in doped perovskite heterostructures: narrow (<20 nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (>120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.

View Article: PubMed Central - PubMed

Affiliation: School of Physical and Mathematical Sciences, Division of Physics and Applied Physics, Nanyang Technological University, 637371 Singapore.

ABSTRACT
Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear. Examining LaAlO₃/SrTiO₃ heterostructures at previously unexplored carrier densities n(2D) ≥ 6.9 × 10(14) cm(-2), we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential dxz,yz orbital occupancy extending over at least 100 nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO₃ emerge simultaneously at higher n(2D). We distinguish three areas in doped perovskite heterostructures: narrow (<20 nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (>120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.

No MeSH data available.


Related in: MedlinePlus

Electronic structure, orbital character and depth-dependent phase emergence at the LaAlO3/SrTiO3 interface.(a–c), Schematics illustrating the phase and carrier distributions for sample A (a), B at low Vg (b) and B at large Vg (c). The approximate local carrier density within the SrTiO3 is indicated by the colour shading: pale yellow denotes undoped bulk SrTiO3, while higher carrier density regions are either red (dxy), green (dxz,yz) or brown (degenerate dxy,xz,yz) depending on the dominant orbital character. dxy ferromagnetism is present regardless of the carrier density, but remains tightly confined to the interface20, i.e. at the top of the red zone. For comparison, we also plot the calculated orbital occupancies for the first ten TiO2 layers below the interface at n2D = 3 × 1013 (a), 3 × 1014 (b) and 8 × 1014 cm−2 (c). The index “1” refers to the TiO2 layer closest to the interface. Red and green bars correspond to dxy and dxz,yz orbitals respectively. (d), Qualitative illustration of the depth-dependent influence of field-effect doping on the local carrier density, which we deduce from our transport data. The line colour indicates the variation in the dominant orbital character with depth. (e),(f), Cartoon Fermi surfaces of the sub-interfacial high-mobility dxz,yz electron gas (e) and the bulk doped SrTiO3 (f) which develops progressively for large n2D.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4061544&req=5

f4: Electronic structure, orbital character and depth-dependent phase emergence at the LaAlO3/SrTiO3 interface.(a–c), Schematics illustrating the phase and carrier distributions for sample A (a), B at low Vg (b) and B at large Vg (c). The approximate local carrier density within the SrTiO3 is indicated by the colour shading: pale yellow denotes undoped bulk SrTiO3, while higher carrier density regions are either red (dxy), green (dxz,yz) or brown (degenerate dxy,xz,yz) depending on the dominant orbital character. dxy ferromagnetism is present regardless of the carrier density, but remains tightly confined to the interface20, i.e. at the top of the red zone. For comparison, we also plot the calculated orbital occupancies for the first ten TiO2 layers below the interface at n2D = 3 × 1013 (a), 3 × 1014 (b) and 8 × 1014 cm−2 (c). The index “1” refers to the TiO2 layer closest to the interface. Red and green bars correspond to dxy and dxz,yz orbitals respectively. (d), Qualitative illustration of the depth-dependent influence of field-effect doping on the local carrier density, which we deduce from our transport data. The line colour indicates the variation in the dominant orbital character with depth. (e),(f), Cartoon Fermi surfaces of the sub-interfacial high-mobility dxz,yz electron gas (e) and the bulk doped SrTiO3 (f) which develops progressively for large n2D.

Mentions: To understand the origin of these in-plane SdH oscillations, we calculate the evolution of the sub-interfacial orbital occupancy (which determines the FS symmetry) with increasing n2D. The majority of electronic structure calculations for LaAlO3/SrTiO3 to date have only considered the first few layers below the interface for n2D ≤ 1014 cm−2 and are of limited use in our heterostructures. We have therefore performed first-principles calculations of the depth-dependent band structure in LaAlO3/SrTiO3 for n2D = 3 × 1013, 3 × 1014 and 8 × 1014 cm−2, specifically chosen to approach our experimental n2D in samples A, B (Vg ~ 0) and B (Vg > 0) respectively. Our calculated orbital occupancies are plotted in Fig. 3a and can also be seen in Fig. 4a–c: although computational power limits us to considering the first 10 unit cells below the interface, this is already sufficient to reveal the FS anisotropy responsible for our in-plane SdH effect.


Long-range electronic reconstruction to a dxz,yz-dominated Fermi surface below the LaAlO₃/SrTiO₃ interface.

Petrović AP, Paré A, Paudel TR, Lee K, Holmes S, Barnes CH, David A, Wu T, Tsymbal EY, Panagopoulos C - Sci Rep (2014)

Electronic structure, orbital character and depth-dependent phase emergence at the LaAlO3/SrTiO3 interface.(a–c), Schematics illustrating the phase and carrier distributions for sample A (a), B at low Vg (b) and B at large Vg (c). The approximate local carrier density within the SrTiO3 is indicated by the colour shading: pale yellow denotes undoped bulk SrTiO3, while higher carrier density regions are either red (dxy), green (dxz,yz) or brown (degenerate dxy,xz,yz) depending on the dominant orbital character. dxy ferromagnetism is present regardless of the carrier density, but remains tightly confined to the interface20, i.e. at the top of the red zone. For comparison, we also plot the calculated orbital occupancies for the first ten TiO2 layers below the interface at n2D = 3 × 1013 (a), 3 × 1014 (b) and 8 × 1014 cm−2 (c). The index “1” refers to the TiO2 layer closest to the interface. Red and green bars correspond to dxy and dxz,yz orbitals respectively. (d), Qualitative illustration of the depth-dependent influence of field-effect doping on the local carrier density, which we deduce from our transport data. The line colour indicates the variation in the dominant orbital character with depth. (e),(f), Cartoon Fermi surfaces of the sub-interfacial high-mobility dxz,yz electron gas (e) and the bulk doped SrTiO3 (f) which develops progressively for large n2D.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061544&req=5

f4: Electronic structure, orbital character and depth-dependent phase emergence at the LaAlO3/SrTiO3 interface.(a–c), Schematics illustrating the phase and carrier distributions for sample A (a), B at low Vg (b) and B at large Vg (c). The approximate local carrier density within the SrTiO3 is indicated by the colour shading: pale yellow denotes undoped bulk SrTiO3, while higher carrier density regions are either red (dxy), green (dxz,yz) or brown (degenerate dxy,xz,yz) depending on the dominant orbital character. dxy ferromagnetism is present regardless of the carrier density, but remains tightly confined to the interface20, i.e. at the top of the red zone. For comparison, we also plot the calculated orbital occupancies for the first ten TiO2 layers below the interface at n2D = 3 × 1013 (a), 3 × 1014 (b) and 8 × 1014 cm−2 (c). The index “1” refers to the TiO2 layer closest to the interface. Red and green bars correspond to dxy and dxz,yz orbitals respectively. (d), Qualitative illustration of the depth-dependent influence of field-effect doping on the local carrier density, which we deduce from our transport data. The line colour indicates the variation in the dominant orbital character with depth. (e),(f), Cartoon Fermi surfaces of the sub-interfacial high-mobility dxz,yz electron gas (e) and the bulk doped SrTiO3 (f) which develops progressively for large n2D.
Mentions: To understand the origin of these in-plane SdH oscillations, we calculate the evolution of the sub-interfacial orbital occupancy (which determines the FS symmetry) with increasing n2D. The majority of electronic structure calculations for LaAlO3/SrTiO3 to date have only considered the first few layers below the interface for n2D ≤ 1014 cm−2 and are of limited use in our heterostructures. We have therefore performed first-principles calculations of the depth-dependent band structure in LaAlO3/SrTiO3 for n2D = 3 × 1013, 3 × 1014 and 8 × 1014 cm−2, specifically chosen to approach our experimental n2D in samples A, B (Vg ~ 0) and B (Vg > 0) respectively. Our calculated orbital occupancies are plotted in Fig. 3a and can also be seen in Fig. 4a–c: although computational power limits us to considering the first 10 unit cells below the interface, this is already sufficient to reveal the FS anisotropy responsible for our in-plane SdH effect.

Bottom Line: However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear.Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO₃ emerge simultaneously at higher n(2D).We distinguish three areas in doped perovskite heterostructures: narrow (<20 nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (>120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.

View Article: PubMed Central - PubMed

Affiliation: School of Physical and Mathematical Sciences, Division of Physics and Applied Physics, Nanyang Technological University, 637371 Singapore.

ABSTRACT
Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear. Examining LaAlO₃/SrTiO₃ heterostructures at previously unexplored carrier densities n(2D) ≥ 6.9 × 10(14) cm(-2), we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential dxz,yz orbital occupancy extending over at least 100 nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO₃ emerge simultaneously at higher n(2D). We distinguish three areas in doped perovskite heterostructures: narrow (<20 nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far (>120 nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.

No MeSH data available.


Related in: MedlinePlus