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.
Highlights
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
We have recently demonstrated that crystal symmetry is an extra degree of freedom to realize different 2DEG band reconstructions at the LaAlO3/SrTiO3 interface, by imposing distinctive orbital hierarchies on (001)- and (110)oriented quantum wells and enabling the selective occupancy of states of different symmetry[24]
We have uncovered that the degeneracy within the t2g sub-band—which forms the backbone of the 2DEG structure in LaAlO3/SrTiO3 wells—is broken in reversed ways depending on the crystal orientation: for (001)-oriented 2DEGs the dxy orbitals have the lowest energy, while along (110) the bottommost levels have instead a dxz/dyz character[24]
Summary
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. 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. The selective confinement of electrons within planes of different crystal orientation expands vigorously the possibility of finetuning the 2DEG sub-band hierarchy and, thereof, the physical properties Along this line, we have recently demonstrated that crystal symmetry is an extra degree of freedom to realize different 2DEG band reconstructions at the LaAlO3/SrTiO3 interface, by imposing distinctive orbital hierarchies on (001)- and (110)oriented quantum wells and enabling the selective occupancy of states of different symmetry[24]. These findings open fresh perspectives to understand the fundamental connection between orbital symmetry and the electronic phases at LaAlO3/ SrTiO3 interfaces
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