Abstract
Interaction between electrons has long been a focused topic in condensed-matter physics since it has led to the discoveries of astonishing phenomena, for example, high-Tc superconductivity and colossal magnetoresistance (CMR) in strongly-correlated materials. In the study of strongly-correlated perovskite oxides, Nb-doped SrTiO3 (Nb:SrTiO3) has been a workhorse not only as a conducting substrate, but also as a host possessing high carrier mobility. In this work, we report the observations of large linear magnetoresistance (LMR) and the metal-to-insulator transition (MIT) induced by magnetic field in heavily-doped Nb:STO (SrNb0.2Ti0.8O3) epitaxial thin films. These phenomena are associated with the interplay between the large classical MR due to high carrier mobility and the electronic localization effect due to strong spin-orbit coupling, implying that heavily Nb-doped Sr(Nb0.2Ti0.8)O3 is promising for the application in spintronic devices.
Highlights
Since the first report of linear magnetoresistance (LMR) in Bi crystals[18], LMR have attracted much interest because MR is expected to be an even function of B owing to symmetry
In the quantum limit where the Landau level spacing is much larger than the thermal energy ( ωc/kBT 1, where, ωc, and kB are reduced Planck constant (h/2π), cyclotron frequency, and Boltzmann constant, respectively), only the lowest Landau level is occupied by electrons leading to the LMR
Note that the model well describes the observed LMR resulting in an estimation of the fitting parameters, Bφ = 0.112 T and BSO = 5.618 T. These values are consistent with the result previously obtained in the LaAlO3/SrTiO3 heterojunction in a high carrier density regime induced by the electric field effect[40], supporting the assumed model (Δρ =ΔρWAL +Δρorb.) as the origin of the observed LMR
Summary
The observed high μ implies that there is a change in the transport mechanism or in the electronic band structure of the heavily-doped Nb:STO films. A. Abrikosov showed that the LMR could be observed at high T with low B under assumptions of (1) a gapless semiconductor with a linear energy vs momentum (E vs k) relation and (2) inhomogeneous carrier distribution[19,29].
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