167 research outputs found
Universality of Electron Mobility in LaAlO/SrTiO and bulk SrTiO
Metallic LaAlO/SrTiO (LAO/STO) interfaces attract enormous attention,
but the relationship between the electron mobility and the sheet electron
density, , is poorly understood. Here we derive a simple expression for
the three-dimensional electron density near the interface, , as a
function of and find that the mobility for LAO/STO-based interfaces
depends on in the same way as it does for bulk doped STO. It is known
that undoped bulk STO is strongly compensated with background donors and acceptors. In intentionally doped
bulk STO with a concentration of electrons background impurities
determine the electron scattering. Thus, when it is natural to see
in LAO/STO the same mobility as in the bulk. On the other hand, in the bulk
samples with the mobility collapses because scattering happens on
intentionally introduced donors. For LAO/STO the polar catastrophe
which provides electrons is not supposed to provide equal number of random
donors and thus the mobility should be larger. The fact that the mobility is
still the same implies that for the LAO/STO the polar catastrophe model should
be revisited.Comment: 4 pages and 1 figur
Quantization of Hall Resistance at the Metallic Interface between an Oxide Insulator and SrTiO
The two-dimensional metal forming at the interface between an oxide insulator
and SrTiO3 provides new opportunities for oxide electronics. However, the
quantum Hall effect, one of the most fascinating effects of electrons confined
in two dimensions, remains underexplored at these complex oxide
heterointerfaces. Here, we report the experimental observation of quantized
Hall resistance in a SrTiO3 heterointerface based on the modulation-doped
amorphous-LaAlO/SrTiO heterostructure, which exhibits both high
electron mobility exceeding 10000 cm/Vs and low carrier density on the
order of ~10 cm. Along with unambiguous Shubnikov-de Haas
oscillations, the spacing of the quantized Hall resistance suggests that the
interface is comprised of a single quantum well with ten parallel conducting
two-dimensional subbands. This provides new insight into the electronic
structure of conducting oxide interfaces and represents an important step
towards designing and understanding advanced oxide devices
Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition
Evidence of weak superconductivity at the room-temperature grown LaAlO<sub>3</sub>/SrTiO<sub>3</sub> interface
The two-dimensional electron gas at the crystalline LaAlO3/SrTiO3 (c-LAO/STO) interface has sparked large interest due to its exotic properties, including an intriguing gate-tunable superconducting phase. While there is growing evidence of pronounced spatial inhomogeneity in the conductivity at STO-based interfaces, the consequences for superconductivity remain largely unknown. We study interfaces based on amorphous LAO top layers grown at room temperature (a-LAO/STO) and demonstrate a superconducting phase similar to c-LAO/STO, however, with a gate-tunable critical temperature of 460 mK. The dependence of the superconducting critical current on temperature, magnetic field, and back-gate-controlled doping is found to be consistently described by a model of a random array of Josephson-coupled superconducting domains
High performance magnetocaloric perovskites for magnetic refrigeration
et al.We have applied mixed valance manganite perovskites as magnetocaloric materials in a magnetic refrigeration device. Relying on exact control of the composition and a technique to process the materials into single adjoined pieces, we have observed temperature spans above 9 K with two materials. Reasonable correspondence is found between experiments and a 2D numerical model, using the measured magnetocaloric properties of the two materials as input. © 2012 American Institute of Physics.The authors would like to acknowledge the support of the Programme Commission on Energy and Environment (EnMi) (Contract No. 2104-06-0032) which is part of the Danish Council for Strategic Research.Peer Reviewe
Patterning of high mobility electron gases at complex oxide interfaces
Oxide interfaces provide an opportunity for electronics. However, patterning
of electron gases at complex oxide interfaces is challenging. In particular,
patterning of complex oxides while preserving a high electron mobility remains
underexplored and inhibits the study of quantum mechanical effects where
extended electron mean free paths are paramount. This letter presents an
effective patterning strategy of both the amorphous-LaAlO/SrTiO
(a-LAO/STO) and modulation-doped amorphous-
LaAlO/LaSrMnO/SrTiO (a-LAO/LSM/STO) oxide
interfaces. Our patterning is based on selective wet etching of amorphous-LSM
(a-LSM) thin films which acts as a hard mask during subsequent depositions.
Strikingly, the patterned modulation-doped interface shows electron mobilities
up to ~8,700 cm/Vs at 2 K, which is among the highest reported values for
patterned conducting complex oxide interfaces that usually are ~1,000 cm/Vs
at 2 K
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