Electrical Transport Anisotropy Controlled by Oxygen Vacancy Concentration in (111) LaAlO<sub>3</sub>/SrTiO<sub>3</sub> Interface Structures

Davis, Samuel; Huang, Zhen; Han, Kun; Ariando, Ariando; Venkatesan, T.; Chandrasekhar, Venkat

doi:10.1002/admi.201600830

Cited by 16 publications

(44 citation statements)

References 23 publications

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“…2(a), evidencing a clear metallic behavior and absence of carrier localization down to 1.5 K. At this temperature the back gate voltage is swept to the maximum applied voltage (90 V) and back to 0 V. At variance with previous reports, we observed no hysteretic or anisotropic transport behavior attributed to the presence of oxygen vacancies [19]. All further measurements presented in this work are shown for one Hall bar recorded at a fixed back gate voltage of 30 V. The detailed investigation of the evolution of the transport properties with electrostatic doping shall be discussed elsewhere.…”

contrasting

confidence: 43%

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

et al. 2017

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contrasting

confidence: 43%

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

et al. 2017

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“…The measurements were carried out in a Kelvinox MX100 dilution fridge with a base temperature of 40 mK using standard 4-probe ac measurements at a frequency of 3 Hz. The ac excitation current was ∼ 10 nA at millikelvin temperatures and ∼ 100 nA at 4.2 K. Unlike in the case of (111) LAO/STO samples, 13 we did not observe any significant anisotropy in the electrical transport properties between Hall bars aligned along the two surface crystal directions (Fig. 1(c)).…”

Section: 29mentioning

confidence: 46%

“…12,13,[16][17][18] The (111) oriented interface has also been predicted to show novel topological phases, given that the surface Ti atoms in STO form a honeycomb lattice that hosts orbitals with hexagonal symmetry.…”

mentioning

confidence: 99%

Electrostatic tuning of magnetism at the conducting (111) (La0.3Sr0.7)(Al0.65Ta0.35)/SrTiO3 interface

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Huang

Han

et al. 2017

Applied Physics Letters

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We present measurements of the low temperature electrical transport properties of the two dimensional carrier gas that forms at the interface of (111) (La 0.3 Sr 0.7 )(Al 0.65 Ta 0.35 )/SrTiO 3 (LSAT/STO) as a function of applied back gate voltage, V g . As is found in (111) LaAlO 3 /SrTiO 3 interfaces, the low-field Hall coefficient is electron-like, but shows a sharp reduction in magnitude below V g ∼ 20 V, indicating the presence of holelike carriers in the system. This same value of V g correlates approximately with the gate voltage below which the magnetoresistance evolves from nonhysteretic to hysteretic behavior at millikelvin temperatures, signaling the onset of magnetic order in the system. We believe our results can provide insight into the mechanism of magnetism in SrTiO 3 based systems.For more than ten years, the two dimensional carrier gas in SrTiO 3 (STO) based heterostructures has provided us with a model system to study a wide variety of physical phenomena, such as magnetism, superconductivity, spinorbit interaction, and localization effects. [1][2][3][4][5][6][7] Adding to the interest is the fact that these interfacial phenomena can be tuned by a range of experimental handles, including applied electric fields, 3 oxygen partial pressure during growth, 5,8,9 capping layers, 10 post growth annealing treatment, 11,12 crystal orientation, 14 and strain. 15 So far, most studies on these heterostructures have focused on LaAlO 3 (LAO) deposited on a (001) oriented STO substrate. However, it was recently discovered that changing the surface crystal orientation can vastly change the properties of the carrier gas.14 In particular, a tunable anisotropy in transport parameters was observed in (110) and (111) oriented LAO/STO. 12,13,[16][17][18] The (111) oriented interface has also been predicted to show novel topological phases, given that the surface Ti atoms in STO form a honeycomb lattice that hosts orbitals with hexagonal symmetry. 19-23(La 0.3 Sr 0.7 )(Al 0.65 Ta 0.35 ) (LSAT) is a commonly used substrate for the growth of other perovskite films. When LSAT is grown on STO, a two-dimensional carrier gas forms at the LSAT/STO interface.24 LSAT has a band gap of 4.9 eV, 25 smaller than the LAO band gap of 5.6 eV, 26 which can affect the relative importance of the different mechanisms contributing to the formation of the conducting gas. LSAT has a 1 % lattice mismatch with STO, as opposed to a 3 % mismatch in the case of LAO, which means the interfacial STO layers experience a smaller strain in the case of LSAT/STO. Also, unlike LAO, but similar to STO, LSAT undergoes a cubic to tetragonal transition at about 100 K, 27,28 which is also expected to reduce strain effects. Earlier work on (001) LAO/STO interfaces 15 demonstrated that strain at the interface can drastically change conduction, whereas recent studies of LSAT grown on (001) STO suggested that the lower strain compared to LAO significantly increased the carrier mobility.24,29 However, there have been only a few transport experiments performed ...

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“…[17][18][19][20] Here we show that the magnetoresistance at or in the superconducting state is hysteretic and also anisotropic. As with the (001) LAO/STO devices, the presence of a hysteretic magnetoresistance (MR) in the (111) LAO/STO devices indicates magnetism coexisting with superconductivity.…”

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confidence: 60%

Magnetoresistance in the superconducting state at the (111) LaAlO3/SrTiO3 interface

et al. 2017

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Condensed matter systems that simultaneously exhibit superconductivity and ferromagnetism are rare due the antagonistic relationship between conventional spin-singlet superconductivity and ferromagnetic order. In materials in which superconductivity and magnetic order is known to coexist (such as some heavy-fermion materials), the superconductivity is thought to be of an unconventional nature. Recently, the conducting gas that lives at the interface between the perovskite band insulators LaAlO3 (LAO) and SrTiO3 (STO) has also been shown to host both superconductivity and magnetism. Most previous research has focused on LAO/STO samples in which the interface is in the (001) crystal plane. Relatively little work has focused on the (111) crystal orientation, which has hexagonal symmetry at the interface, and has been predicted to have potentially interesting topological properties, including unconventional superconducting pairing states. Here we report measurements of the magnetoresistance of (111) LAO/STO heterostructures at temperatures at which they are also superconducting. As with the (001) structures, the magnetoresistance is hysteretic, indicating the coexistence of magnetism and superconductivity, but in addition, we find that this magnetoresistance is anisotropic. Such an anisotropic response is completely unexpected in the superconducting state, and suggests that (111) LAO/STO heterostructures may support unconventional superconductivity.

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Electrical Transport Anisotropy Controlled by Oxygen Vacancy Concentration in (111) LaAlO₃/SrTiO₃ Interface Structures

Cited by 16 publications

References 23 publications

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

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

Electrostatic tuning of magnetism at the conducting (111) (La0.3Sr0.7)(Al0.65Ta0.35)/SrTiO3 interface

Magnetoresistance in the superconducting state at the (111) LaAlO3/SrTiO3 interface

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Electrical Transport Anisotropy Controlled by Oxygen Vacancy Concentration in (111) LaAlO3/SrTiO3 Interface Structures

Cited by 16 publications

References 23 publications

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

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

Electrostatic tuning of magnetism at the conducting (111) (La0.3Sr0.7)(Al0.65Ta0.35)/SrTiO3 interface

Magnetoresistance in the superconducting state at the (111) LaAlO3/SrTiO3 interface

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Electrical Transport Anisotropy Controlled by Oxygen Vacancy Concentration in (111) LaAlO₃/SrTiO₃ Interface Structures