M. Ben Shalom

Tel Aviv University, Tell Afif, Tel Aviv, Israel

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Publications (14)42.65 Total impact

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    M. Ben Shalom, I. Neder, A. Palevski, Y. Dagan
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    ABSTRACT: The rich phase diagram of the two dimensional electron gas (2DEG) at the \STO/\LAO interface is probed using Hall and longitudinal resistivity. Thanks to a special bridge design we are able to tune through the superconducting transition temperature T$_c$ and to mute superconductivity by either adding or removing carriers in a gate bias range of a few volts. Hall signal measurements pinpoint the onset of population of a second mobile band right at the carrier concentration where maximum superconducting T$_c$ and critical field H$_c$ occur. These results emphasize the advantages of our design, which can be applied to many other two dimensional systems assembled on top of a dielectric substrate with high permittivity.
    02/2014;
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    ABSTRACT: Sharp interfaces can host phenomena that are absent in their constituting materials. By depositing a thin layer of LaAlO3 on top of SrTiO3, the interface between these two band-insulator is highly conducting. Conductivity emerges only for TiO2 termination and above a critical LaAlO3 thickness of 4 unit cells, pointing to the importance of the polar structure. The transition, from insulating to high mobility electron gas, can be controlled continuously by gate voltage, thus enabling a careful study of the dependence of system properties on charge density. Carrier-controlled two-dimensional superconductivity, and magnetic hysteresis were observed between the two non-magnetic oxides. We have found anisotropic magnetoresistance (AMR) in our samples, an outcome of magnetic scattering, which affect the transport through the spin orbit (SO) interaction, and coexists with superconductivity. Gate bias enables tuning the SO energy, which dominates the magnetotransport properties. The exceptionally large amplitude and sign of the AMR suggests a Rashba-type SO coupling. The different AMR characteristics for Nb doped SrTiO3, a symmetric non-polar with similar resistivity and carrier density, demonstrates the significant role of interface polarity for its magnetic properties.
    03/2013;
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    ABSTRACT: We report on resistivity and Hall measurements performed on a series of narrow mesa devices fabricated from LaAlO_3/SrTiO_3 single interface heterostructure with a bridge width range of 1.5-10 microns. Upon applying back-gate voltage of the order of a few Volts, a strong increase in the sample resistance (up to factor of 35) is observed, suggesting a relatively large capacitance between the Hall-bar and the gate. The high value of this capacitance is due to the device geometry, and can be explained within an electrostatic model using the Thomas Fermi approximation. The Hall coefficient is sometimes a non-monotonic function of the gate voltage. This behavior is inconsistent with a single conduction band model. We show that a theoretical two-band model is consistent with this transport behavior, and indicates a metal to insulator transition in at least one of these bands.
    Physical review. B, Condensed matter 01/2013; 87(12). · 3.66 Impact Factor
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    ABSTRACT: We report the observation of weak magnetism in superlattices of LaAlO_{3}/SrTiO_{3} using β-detected nuclear magnetic resonance. The spin lattice relaxation rate of ^{8}Li in superlattices with a spacer layers of 8 and 6 unit cells of LaAlO_{3} exhibits a strong peak near ∼35 K, whereas no such peak is observed in a superlattice with spacer layer thickness of 3 unit cells. We attribute the observed temperature dependence to slowing down of weakly coupled electronic moments at the LaAlO_{3}/SrTiO_{3} interface. These results show that the magnetism at the interface depends strongly on the thickness of the spacer layer, and that a minimal thickness of ∼4-6 unit cells is required for the appearance of magnetism. A simple model is used to determine that the observed relaxation is due to small fluctuating moments (∼0.002μ_{B}) in the two samples with a larger LaAlO_{3} spacer thickness.
    Physical Review Letters 12/2012; 109(25):257207. · 7.73 Impact Factor
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    ABSTRACT: Anisotropic magnetoresistance and negative magnetoresistance for in-plane fields are compared for the LaAlO3 /SrTiO3 interface and the symmetric Nb-doped SrTiO3 heterostructure. Both effects are exceptionally strong in LaAlO3 /SrTiO3 . We analyze their temperature, magnetic field and gate voltage dependencies and find them to arise from a Rashba type spin-orbit coupling with magnetic scatterers that have two contributions to their potential: spin exchange and Coulomb interaction. Atomic spin-orbit coupling is sufficient to explain the small effects observed in Nb-doped SrTiO3 . These results clarify contradicting transport interpretations in SrTiO3 -based heterostructures.
    Physical review. B, Condensed matter 07/2012; 86(12). · 3.66 Impact Factor
  • S. Lerer, M. Ben Shalom, G. Deutscher, Y. Dagan
    Physical review. B, Condensed matter 09/2011; 84. · 3.66 Impact Factor
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    ABSTRACT: The magnetoresistance as a function of temperature and field for atomically flat interfaces between 8 unit cells of LaAlO3 and SrTiO3 is reported. Anomalous anisotropic behavior of the magnetoresistance is observed below 30 K for superconducting samples with carrier concentration of 3.5\times10^13 cm^-2 . We associate this behavior to a magnetic order formed at the interface.
    Physica C Superconductivity 01/2011; 470. · 0.72 Impact Factor
  • M Ben Shalom, A Ron, A Palevski, Y Dagan
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    ABSTRACT: Quantum magnetic oscillations in SrTiO3/LaAlO3 interface are observed in the magnetoresistance. We study their frequency as a function of gate voltage and the evolution of their amplitude with temperature. The data are consistent with the Shubnikov-de Haas theory. The Hall resistivity ρ(xy) is nonlinear at low magnetic fields. ρ(xy) is fitted assuming multiple carrier contributions. We infer the density of the mobile charge carriers from the oscillations frequency and from Hall measurements. The comparison between these densities suggests multiple valley and spin degeneracy. The small amplitude of the oscillation is discussed in the framework of the multiple band scenario.
    Physical Review Letters 11/2010; 105(20):206401. · 7.73 Impact Factor
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    ABSTRACT: The two dimensional electron gas formed between the two band insulators SrTiO3 and LaAlO3 exhibits a variety of interesting physical properties which make it an appealing material for use in future spintronics and/or quantum computing devices. For this kind of applications electrons have to retain their phase memory for sufficiently long times or length. Using a mesoscopic size device we were able to extract the phase coherence length, and its temperature variation. We find the dephasing rate to have a power law dependence on temperature. The power depends on the temperature range studied and sheet resistance as expected from dephasing due to strong electron-electron interactions. Comment: Submitted to Phys. Rev B
    Physical review. B, Condensed matter 09/2010; · 3.66 Impact Factor
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    M. Ben Shalom, A. Ron, A. Palevski, Y. Dagan
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    ABSTRACT: Quantum magnetic oscillations in SrTiO3/\LaAlO3 interface are observed. The evolution of their frequency and amplitude at various gate voltages and temperatures is studied. The data are consistent with the Shubnikov de-Haas theory. The Hall resistivity rho exhibits nonlinearity at low magnetic field. It is fitted assuming multiple carrier contributions. The comparison between the mobile carrier density inferred from the Hall data and the oscillation frequency suggests multiple valley and spin degeneracy. The small amplitude of the oscillations is discussed in the framework of the multiple band scenario.
    08/2010;
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    ABSTRACT: The superconducting transition temperature T{c} of the SrTiO{3}/LaAlO{3} interface was varied by the electric field effect. The anisotropy of the upper critical field and the normal-state magnetotransport were studied as a function of gate voltage. The spin-orbit coupling energy epsilon{SO} is extracted. This tunable energy scale is used to explain the strong gate dependence of the mobility and of the anomalous Hall signal observed. Epsilon{SO} follows T{c} for the electric field range under study.
    Physical Review Letters 03/2010; 104(12):126802. · 7.73 Impact Factor
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    ABSTRACT: The sheet resistance as a function of temperature, magnetic field and its orientation for atomically flat SrTiO3/LaAlO3 interfaces with carrier densities of ˜3×1013cm-2 is reported. At low magnetic fields superconductivity is observed below 130 mK. The temperature dependence of the high field magnetoresistance and its strong anisotropy suggest possible magnetic ordering below 35 K. The origin of this ordering and its possible relation to superconductivity are discussed.
    Physical Review B 10/2009; 80(14):140403(R). · 3.66 Impact Factor
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    ABSTRACT: The resistivity as a function of temperature, magnetic field and its orientation for atomically flat SrTiO3\LaAlO3 interfaces with carrier densities of ~3*10^13 cm^-2 is reported. At low magnetic fields superconductivity is observed below 130mK. The temperature dependence of the high field magnetoresistance and its strong anisotropy suggest possible magnetic ordering below 35K. The origin of this ordering and its possible relation to superconductivity are discussed.
    02/2009;