Thermally excited multiband conduction in LaAlO3/SrTiO3 heterostructures exhibiting magnetic scattering (original) (raw)
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Multi-band conduction behaviour at the interface of LaAlO3/SrTiO3 heterostructures
Journal of the Korean Physical Society, 2013
We have measured the Hall resistance and magneto-resistance (MR) of LaAlO3/SrTiO3 heterojunctions at magnetic fields up to 30 T in a temperature range T = 4 K to 70 K. For temperature below 7 K and above 50 K the devices display linear Hall resistance, indicating that one type of charge carriers dominate the transport. For temperatures between 10 K and 40 K, the Hall resistance is strongly non-linear, and is accompanied by a large positive MR, which is governed by the component of magnetic field normal to the interface. This behaviour in the intermediate temperature regime can be related to thermally activated high-mobility carriers.
Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures
Applied Physics Letters, 2013
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Transport and thermoelectric properties of the LaAlO 3 / SrTiO 3 interface
Physical Review B, 2015
The transport and thermoelectric properties of the interface between SrTiO3 and a 26-monolayer thick LaAlO3-layer grown at high oxygen-pressure have been investigated at temperatures from 4.2 K to 100 K and in magnetic fields up to 18 T. We observe two different electron-like charge carriers originating from two electron channels which contribute to transport. We apply a two-carrier model to our transport-data and develop a consistent model for the termoelectric tensor. We attribute the deviation from our model in magnetoresistance and thermopower at low temperatures to magnetism arising from the Ti 3+ -atoms at the interface.
Quantum Electrical Transport in Mesoscopic LaAlO 3 /SrTiO 3 Heterostructures
Applied Physics Express, 2013
We report the fabrication and electrical measurements for LaAlO 3 /SrTiO 3 (LAO/STO) heterostructures having various lateral sizes. When the sample size is reduced to the sub-micrometer range, the magnetoconductance (MC) curve deviates from classical parabolic behavior. Instead, a negative MC behavior appears with superimposed conductance fluctuations, which is attributed to weak antilocalization and universal conductance fluctuations. Using the Maekawa-Fukuyama model, the spin-orbit scattering and phase coherence lengths are estimated from the MC data, which are dependent on the gate voltage and temperature. Our comprehensive study shows that LAO/STO heterointerfaces provide a useful platform to explore quantum coherent transport of strongly correlated electrons. #
Two-Dimensional Quantum Oscillations of the Conductance at LaAlO_{3}/SrTiO_{3} Interfaces
Physical Review Letters, 2010
We report on a study of magnetotransport in LaAlO3/SrTiO3 interfaces characterized by mobilities of the order of several thousands cm 2 /Vs. We observe Shubnikov-de Haas oscillations that indicate a two-dimensional character of the Fermi surface. The frequency of the oscillations signals a multiple sub-bands occupation in the quantum well or a multiple valley configuration. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m * 1.45 me. An electric field applied in the back-gate geometry increases the mobility, the carrier density and the oscillation frequency.
Multiple conducting carriers generated in LaAlO3/SrTiO3 heterostructures
Applied Physics Letters, 2009
We have found that there is more than one type of conducting carriers generated in LaAlO 3 /SrTiO 3 heterostructures by comparing the sheet carrier density and mobility from optical transmission spectroscopy with those from dc-transport measurements. When multiple types of carriers exist, optical characterization dominantly reflects the contribution from the high-density carriers whereas dc-transport measurements may exaggerate the contribution of the high-mobility carriers even though they are present at low-density. Since the low-temperature mobilities determined by dc-transport in the LaAlO 3 /SrTiO 3 heterostructures are much higher than those extracted by optical method, we attribute the origin of high-mobility transport to the low-density conducting carriers.
Physical Review B, 2011
We report transport measurements, including: Hall, Seebeck and Nernst Effect. All these transport properties exhibit anomalous field and temperature dependences, with a change of behavior observed at about H ∼ 1.5T and T ∼ 15K. We were able to reconcile the low-temperature-low-field behavior of all transport properties using a simple two band analysis. A more detailed model is required in order to explain the high magnetic field regime.
Multiple conducting carriers generated in LaAlO[sub 3]/SrTiO[sub 3] heterostructures
Applied Physics Letters, 2009
We have found that there is more than one type of conducting carriers generated in LaAlO 3 /SrTiO 3 heterostructures by comparing the sheet carrier density and mobility from optical transmission spectroscopy with those from dc-transport measurements. When multiple types of carriers exist, optical characterization dominantly reflects the contribution from the high-density carriers whereas dc-transport measurements may exaggerate the contribution of the high-mobility carriers even though they are present at low-density. Since the low-temperature mobilities determined by dc-transport in the LaAlO 3 /SrTiO 3 heterostructures are much higher than those extracted by optical method, we attribute the origin of high-mobility transport to the low-density conducting carriers. * seos@ornl.gov † hnlee@ornl.gov
Nature Communications, 2014
In condensed matter physics the quasi two-dimensional electron gas at the interface of two different insulators, polar LaAlO3 on non-polar SrTiO3 (LaAlO3/SrTiO3) is a spectacular and surprising observation. This phenomenon is LaAlO3 film thickness-dependent and may be explained by the polarization catastrophe model, in which a charge transfer of 0.5efrom the LaAlO3 film into the LaAlO3/SrTiO3 interface is expected. Here we show that in conducting samples (≥4 unit cells of LaAlO3) there is indeed a ~0.5etransfer from LaAlO3 into the LaAlO3/SrTiO3 interface by studying the optical conductivity in a broad energy range (0.5-35 eV). Surprisingly, in insulating samples (≤3 unit cells of LaAlO3) a redistribution of charges within the polar LaAlO3 sub-layers (from AlO2 to LaO) as large as ~0.5eis observed, with no charge transfer into the interface.
ACS applied materials & interfaces, 2016
Clarification of the role of magnetic ordering and scattering in two-dimensional electron gas has become increasingly important to understand the transport and magnetic behavior in the LaAlO3 (LAO)/SrTiO3 (STO) heterostructures. In this work, we report the sheet resistance of the LAO/STO heterostructures as functions of temperature, magnetic field, and field orientation. An unexpected resistance minimum was discovered at ∼10 K under a sufficiently high in-plane magnetic field. An anisotropic magnetoresistance (MR) is clearly identified, indicating the presence of magnetic scattering which may be related to the interaction between itinerant electrons and localized magnetic moments in the LaAlO3/SrTiO3 heterostructures. It is believed that the high concentration of oxygen vacancies induced by the ultralow oxygen partial pressure during the deposition process plays a predominant role in the occurrence of the anisotropic MR.