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Santander-Syro, A. F.; Bareille, C.; Fortuna, F.; Copie, O.; Gabay, M.; Bertran, F.; Taleb‐Ibrahimi, A.; Fèvre, P. Le; Herranz, G.; Reyren, Nicolas; Bibès, Manuel; Barthélémy, A.; Lecoeur, Ph.; Guevara, Javier; Rozenberg, M. J.

doi:10.1103/physrevb.86.121107

Cited by 94 publications

(123 citation statements)

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“…One of the probably most puzzling aspects is that, at the moment, STO seems to be quite a unique and fundamental ingredient in the formation of the q2DES. However, from surface science we are learning about other potential materials, which can replace STO, like tantalates (KTaO 3 [84]), forming at their surfaces q2DES's.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Salluzzo

2015

Oxide Thin Films, Multilayers, and Nanocomposites

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The conducting quasi-two dimensional electron system (q2DES) formed at the interface between LaAlO 3 and SrTiO 3 band insulators is confronting the condensed matter physics community with new paradigms. While the mechanism for the formation of the q2DES is debated, new conducting interfaces have been discovered paving the way to possible applications in electronics, spintronics and optoelectronics. This chapter is an overview of the research on the LAO/STO system, presenting some of the most important results obtained in the last decade to clarify the mechanism of formation of the q2DES at the oxide interfaces and its peculiar electronic properties as compared to semiconducting 2D-electron gas.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Salluzzo

2015

Oxide Thin Films, Multilayers, and Nanocomposites

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“…Strontium titanate (SrTiO 3 ), the cornerstone of such oxide-based electronics, is a transparent, nonmagnetic, wide-band-gap insulator in the bulk, and has recently been found to host a surface 2DEG [12][13][14][15]. The most strongly confined carriers within this 2DEG comprise two sub-bands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces [12,13,15].…”

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confidence: 99%

“…In a simple approximation, this field will induce a so-called "Rashba splitting" of the spin states in each subband, with the largest splitting occurring for the most bound subbands. In an ideal surface, the corresponding momentum separation (k R ) will be of the order of k R ≈ 2eF/∆, where ∆ is the gap between the valence and conduction bands [14,18]. For F ∼ 100 MV/m and ∆ ∼ 3.5 eV, typical of the 2DEG at the surface of SrTiO 3 [12,15], the momentum spin splitting at E F is thus expected to be of the order of k R ∼ 6 × 10 −3Å−1 , at the limit of the best resolutions today available in ARPES.…”

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confidence: 99%

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

et al. 2014

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1 Two-dimensional electron gases (2DEGs) forming at the interfaces of transition metal oxides [1][2][3] display a range of properties including tunable insulatorsuperconductor-metal transitions [4][5][6], large magnetoresistance [7], coexisting ferromagnetism and superconductivity [8, 9], and a spin splitting of a few meV [10,11]. Strontium titanate (SrTiO 3 ), the cornerstone of such oxide-based electronics, is a transparent, nonmagnetic, wide-band-gap insulator in the bulk, and has recently been found to host a surface 2DEG [12][13][14][15]. The most strongly confined carriers within this 2DEG comprise two sub-bands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces [12,13,15].Using spin-and angle-resolved photoemission spectroscopy (SARPES), we show that the electron spins in these sub-bands have opposite chiralities. Although the Rashba effect might be expected to give rise to such spin textures, the giant splitting of almost 100 meV at the Fermi level is far larger than anticipated [16,17].Moreover, in contrast to a simple Rashba system, the spin-polarized sub-bands are non-degenerate at the Brillouin zone centre. This degeneracy can be lifted by time-reversal symmetry breaking, implying the possible existence of magnetic order. These results show that confined electronic states at oxide surfaces can be endowed with novel, non-trivial properties that are both theoretically challenging to anticipate and promising for technological applications.The 2DEG at the surface of SrTiO 3 , formed by confined electrons of the t 2g conduction band with Ti-3d character, is universal in the sense that its constituent subbands, their fillings, and their Fermi surfaces are independent of the bulk sample doping and of whether the surfaces are prepared by cleaving [12,13] or by etching and in situ annealing [15]. This 2DEG consists on two light electron subbands dispersing down to about −180 meV and, respectively, −90 meV below the Fermi level (E F ), producing concentric Fermi surfaces around the Brillouin zone center, and heavy shallow subbands dispersing down to about −40 meV, forming ellipsoidal Fermi surfaces [12,13,15].In fact, the 2DEG in SrTiO 3 has been associated with a band-bending of ∼ 300 meV at the surface of the material [12,13,15]. In such a quantum well profile, the most bound light subbands are tightly confined near the surface, while the less bound heavy subbands are more delocalized towards the bulk [12,15]. The present work focuses on resolving the spin 2 structure of the strongly two-dimensional light subbands, which are the most technologically relevant in terms of their carrier concentration and mobility.The surface band-bending of ∼ 300 meV amounts to an electric field F ∼ 100 MV/m confining the conduction electrons near the surface. In a simple approximation, this field will induce a so-called "Rashba splitting" of the spin states in each subband, with the largest splitting occurring for the most bound subbands. In an ideal surface, the corresponding momentum separat...

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“…The origin of surface states in SrTiO 3 and a related material KTaO 3 [4, 5] (STO and KTO for short, respectively) is currently under active investigation [5,6]. Both materials' surface states originate from t 2g -orbitals whose relevant tight-binding parameters for the electronic structure are largely determined, including the one pertaining to the degree of inversion symmetry breaking (ISB) at the surface [5,6].Several features make STO and KTO surface states an ideal ground for the study of Rashba-related phenomena. First is the way that Rashba effects would play out among the several observed bands of differing orbital characters.…”

mentioning

confidence: 99%

“…The discovery of surface electronic states in strontium titanate (SrTiO 3 )[1, 2] has stirred great excitement at the time the material is being viewed as a critical component of the emerging field of oxide electronics [3]. The origin of surface states in SrTiO 3 and a related material KTaO 3 [4, 5] (STO and KTO for short, respectively) is currently under active investigation [5,6]. Both materials' surface states originate from t 2g -orbitals whose relevant tight-binding parameters for the electronic structure are largely determined, including the one pertaining to the degree of inversion symmetry breaking (ISB) at the surface [5,6].…”

mentioning

confidence: 99%

Nature of orbital and spin Rashba coupling in the surface bands ofSrTiO3andKTaO3

Kim

Kang

et al. 2014

Phys. Rev. B

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Tight-binding models for the recently observed surface electronic bands of SrTiO3 and KTaO3 are analyzed with a view to bringing out the relevance of momentum-space chiral angular momentum structures of both orbital and spin origins. Depending on the strength of electric field associated with inversion symmetry breaking at the surface, the orbital and the accompanying spin angular momentum structures reveal complex linear and cubic dependencies in the momentum k (linear and cubic Rashba effects, respectively) in a band-specific manner. Analytical expressions for the cubic orbital and spin Rashba effects are derived by way of unitary transformation technique we developed, and compared to numerical calculations. Due to the C4v symmetry of the perovskite structure the cubic Rashba effect appears as in-plane modulations. The discovery of surface electronic states in strontium titanate (SrTiO 3 )[1, 2] has stirred great excitement at the time the material is being viewed as a critical component of the emerging field of oxide electronics [3]. The origin of surface states in SrTiO 3 and a related material KTaO 3 [4, 5] (STO and KTO for short, respectively) is currently under active investigation [5,6]. Both materials' surface states originate from t 2g -orbitals whose relevant tight-binding parameters for the electronic structure are largely determined, including the one pertaining to the degree of inversion symmetry breaking (ISB) at the surface [5,6].Several features make STO and KTO surface states an ideal ground for the study of Rashba-related phenomena. First is the way that Rashba effects would play out among the several observed bands of differing orbital characters. ARPES measurements up to now [1, 2, 4, 5] did not clearly resolve the Rashba-split bands, presumably due to the smallness of the predicted Rashba parameter [7]. Transport measurements do reveal the Rashba term, of cubic order in momentum, through analysis of the orientation-dependent magneto-resistance data on STO surface [8,9]. Existing theories treat Rashba effects of t 2g -derived bands phenomenologically [6, 10] and cannot, for instance, explain the complex band-specific spin and orbital angular momentum structures observed in the electronic structure calculation [7].It has recently been argued that multi-orbital bands, subject to the surface ISB electric field, must give rise to an entity called the chiral orbital angular momentum (OAM) in momentum space [11,12]. The argument remains valid as long as the crystal field splitting does not quench the multi-orbital degrees of freedom in a given band structure. Such conditions seem to be well met in both STO and KTO, leading to the term ∼ k × E · L where L is the OAM operator for t 2g -orbitals, k is the linear momentum, and E is the surface-normal electric field. The effect was dubbed "orbital Rashba effect" [11] in analogy to the similar chiral structure of spins on the surface [13]. It was shown that pre-existing chiral OAM structure implies the linear Rashba effect upon the inclusion of spin-orb...

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Orbital symmetry reconstruction and strong mass renormalization in the two-dimensional electron gas at the surface of KTaO3

Cited by 94 publications

References 29 publications

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

Nature of orbital and spin Rashba coupling in the surface bands ofSrTiO3andKTaO3

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