Anisotropic magneto-transport properties of electron gases at SrTiO3 (111) and (110) surfaces

Miao, Ludi; Du, Renzhong; Yin, Yuewei; Li, Qi

doi:10.1063/1.4972985

Cited by 40 publications

(44 citation statements)

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“…This is very different from our current results for (111) LAO/STO, which have different dependence on θ and ϕ [ Fig. 5].The AMR study on irradiated STO systems can also exhibit a six-fold AMR effect [36,45]. However, the sign of AMR is always opposite to the AMR observed in an LAO/STO interface (compare Ref.…”

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confidence: 98%

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Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO3/SrTiO3 oxide interface

et al. 2017

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We measured the magnetoresistance of the 2D electron liquid formed at the (111) LaAlO3/SrTiO3 interface. The hexagonal symmetry of the interface is manifested in a six-fold crystalline component appearing in the anisotropic magnetoresistance (AMR) and planar Hall data, which agree well with symmetry analysis we performed. The six-fold component increases with carrier concentration, reaching 15% of the total AMR signal. Our results suggest the coupling between higher itinerant electronic bands and the crystal as the origin of this effect and demonstrate that the (111) oxide interface is a unique hexagonal system with tunable magnetocrystalline effects.Introduction.-The two dimensional electron liquid formed at the (100) interface between the two nonmagnetic insulators LaAlO 3 (LAO) and SrTiO 3 (STO) [1] features numerous properties, such as superconductivity [2,3] and spin-orbit coupling [4,5], which are tunable by a gate voltage. Past studies have shown evidence for magnetic order (possibly co-existing with superconductivity) whose exact character is not yet clear [6][7][8][9][10][11][12][13][14][15], prompting much theoretical activity [16][17][18][19].In-plane anisotropic magnetoresistance (AMR) can be employed as a probe for the magnetic properties of 2D structures, since it is sensitive to spin texture and spin-orbit interaction [20]. In the absence of crystalline anisotropy, rotating the magnetic field in the 2D plane results in a standard two-fold symmetric AMR term that depends on the angle between the magnetic field and the current. Such dependence has been observed in (100) LAO/STO [21][22][23]. It is absent in nonpolar doped STO heterostructure [22] and can hence be related to the Rashba spin-orbit interaction which is expected to be less important in the latter. It has been suggested that an easy axis for magnetization can be observed in the AMR [18], however, the almost square symmetry of the interfacial crystal structure makes it difficult to distinguish between the two-fold term and the crystalline one. Here we explored a different interface, which has a hexagonal in-plane symmetry, namely the (111) LAO/STO heterostructure.The stacking of (111) perovskite ABO 3 layers is AO 3 /B/AO 3 /B [ Fig. 1(a)], and therefore with alternating -3e and +3e charges in LaAlO 3 , whereas -4e and +4e in SrTiO 3 [24]. In addition to the different polar structure compared to the (100) interface, its hexagonal symmetry has been predicted to be a key ingredient for the realization of various nontrivial states [25,26]. Recently, six-fold Fermi contour related to the symmetry of STO (111) surface has been observed by angle resolved photoemission [27,28]. However, a distinct signature of six-fold symmetry of the (111) LAO/STO interface is lacking. In this Rapid Communication we show theoretically and ex- * yodagan@post.tau.ac.il perimentally that a six-fold crystalline cos(6θ) term can be observed in the AMR of the (111) LAO/STO interface. This term depends on carrier concentration, suggesting that coupling between the lat...

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confidence: 98%

“…[21] and Ref. [45] to our results). This indicates that the AMR in irradiated systems results from orbital effects as suggested in Ref.…”

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confidence: 73%

Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO3/SrTiO3 oxide interface

et al. 2017

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“…The 2DES at the (111)LAO/STO interface [11] is an interesting subject of investigation, combining a polar discontinuity at the interface with such a hexagonal lattice. Signatures of the sixfold symmetry related to the (111)STO orientation have recently been observed by angle-resolved photoemission spectroscopy (ARPES) [12,13] and magnetoresistance [14,15] measurements, making the system potentially suitable for exotic time-reversal symmetry breaking superconductivity [16]. Moreover, ARPES measurements at the surface of (111)STO have confirmed a distinct orbital ordering of the t 2g manifold [12], where all the bands are degenerate at the point.…”

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Two-dimensional superconductivity at the (111) LaAlO3/SrTiO3 interface

et al. 2017

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“…Moreover, a Mott insulator as well as an antiferromagnetic correlated ground state have also been predicted in (111) HSs involving strongly correlated oxides [32][33][34][35]. At present, the formation of a 2DEG has already been reported in (111)-oriented LaAlO 3 /SrTiO 3 interfaces [36,37] and in the bare surface of (111) SrTiO 3 crystals [38,39]. Recently (111)-oriented perovskite SLs were synthesized [40,41].…”

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confidence: 92%

Tunable correlated-electron phases in (111) LaAlO3/SrTiO3 band insulator heterostructures

Beltrán

Muñoz

2017

Phys. Rev. B

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Density functional theory calculations reveal the existence of different correlated-electron ground states in (111)-oriented n-type LaAlO 3 /SrTiO 3 symmetric superlattices. They can be tuned by selecting the SrTiO 3 thickness, and range from a trivial metal for thick SrTiO 3 slabs to a Mott-type antiferromagnet in the ultrathin limit. An itinerant ferromagnet and a half-metal phase are also stable in the intermediate region. This remarkable property is a distinct characteristic of (111) perovskite heterostructures and originates from the combined effect of polar discontinuity at the interface, trigonal lattice symmetry, and quantum confinement. While the polar discontinuity promotes the filling of the empty d states of the SrTiO 3 with one electron, the trigonal symmetry dictates that the wave function of the occupied bands spreads over the entire SrTiO 3 slab. Thus, the electron density can be chosen by selecting the number of SrTiO 3 layers. For high densities, symmetry breaking and on-site Coulomb interaction drive the occurrence of correlated-electron ground states. Our results show that low dimensionality can lead to unconventional behavior of oxide heterostructures formed by electronically fairly simple nonmagnetic band insulators, and can open perspectives for the use of LaAlO 3 /SrTiO 3 superlattices grown along the [111] direction to explore quantum phase transitions.

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Anisotropic magneto-transport properties of electron gases at SrTiO3 (111) and (110) surfaces

Cited by 40 publications

References 55 publications

Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO3/SrTiO3 oxide interface

Six-fold crystalline anisotropic magnetoresistance in the (111) LaAlO3/SrTiO3 oxide interface

Two-dimensional superconductivity at the (111) LaAlO3/SrTiO3 interface

Tunable correlated-electron phases in (111) LaAlO3/SrTiO3 band insulator heterostructures

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