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arXiv · 1806.10519

Symmetry breaking at the (111) interfaces of SrTiO${_3}$ hosting a 2D-electron system

G. M. De Luca·R. Di Capua·E. Di Gennaro·A. Sambri·F. Miletto Granozio·G. Ghiringhelli·D. Betto·C. Piamonteze·N. B. Brookes·M. Salluzzo
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Abstract

We used x-ray absorption spectroscopy to study the orbital symmetry and the energy band splitting of (111) LaAlO${_3}$/SrTiO${_3}$ and LaAlO${_3}$/EuTiO${_3}$/SrTiO${_3}$ heterostructures, hosting a quasi two-dimensional electron system (q2DES), and of a Ti-terminated (111) SrTiO${_3}$ single crystal, also known to form a q2DES at its surface. We demonstrate that the bulk tetragonal Ti-3d D${_4}$${_h}$ crystal field is turned into trigonal D${_3}$${_d}$ crystal field in all cases. The symmetry adapted a${_1}$${_g}$ and e${^\pi_g}$ orbitals are non-degenerate in energy and their splitting, \Delta, is positive at the bare STO surface but negative in the heterostructures, where the a${_1}$${_g}$ orbital is lowest in energy. These results demonstrate that the interfacial symmetry breaking induced by epitaxial engineering of oxide interfaces has a dramatic effect on their electronic properties, and it can be used to manipulate the ground state of the q2DES.

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G. M. De Luca, R. Di Capua, E. Di Gennaro, A. Sambri, F. Miletto Granozio, G. Ghiringhelli, D. Betto, C. Piamonteze, N. B. Brookes, M. Salluzzo. 2018-06-27. Symmetry breaking at the (111) interfaces of SrTiO${_3}$ hosting a 2D-electron system. https://doi.org/10.1103/physrevb.98.115143

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