Hysteretic magnetoresistance and thermal bistability in a magnetic two-dimensional hole system

Journal name:
Nature Physics
Volume:
6,
Pages:
955–959
Year published:
DOI:
doi:10.1038/nphys1782
Received
Accepted
Published online

Colossal negative magnetoresistance and the associated field-inducedinsulator-to-metal transition—the most characteristic features of magnetic semiconductors—are observed in n-type rare-earth oxides1 and chalcogenides2, p-type manganites3 and n-type4, 5 and p-type diluted magnetic semiconductors4, 6, as well as in quantum wells of n-type diluted magnetic semiconductors7, 8, 9. Here, we report on magnetotransport studies of Mn-modulation-doped InAs quantum wells, which reveal an insulator-to-metal transition that is driven by a magnetic field and dependent on bias voltage, with abrupt and hysteretic changes of resistance over several orders of magnitude. These phenomena coexist with the quantized Hall effect in high magnetic fields. We show that the exchange coupling between a hole and the parent Mn acceptor produces a magnetic anisotropy barrier that shifts the spin relaxation time of the bound hole to a 100s range in compressively strained quantum wells. This bistability of the individual Mn acceptors explains the hysteretic behaviour while opening prospects for information storing and processing. At high bias voltage another bistability, caused by the overheating of electrons10, gives rise to abrupt resistance jumps.

At a glance

Figures

  1. Results of four-terminal magnetotransport measurements and sample architectures.
    Figure 1: Results of four-terminal magnetotransport measurements and sample architectures.

    a,b Longitudinal resistance (red) and Hall resistance (black) at 1.6K for inverted (a) and normal (b) modulation-doped QW structures showing well-defined Shubnikov–de Haas oscillations and Hall plateaus. In contrast to the normal-doped QW structure (b), the low-field resistivity increases dramatically for the structure with an inverted doping layer (a), indicating strong hole localization. Insets, Schematic layer sequences of the inverted and normal Mn modulation-doped QW structures. The QW consists of a strain-relaxed InGaAs layer with an asymmetrically embedded strained InAs channel.

  2. Temperature dependence of longitudinal resistance of the inversely doped structure in high B fields.
    Figure 2: Temperature dependence of longitudinal resistance of the inversely doped structure in high B fields.

    The longitudinal resistance Rxx along the directions shows well-developed Shubnikov–de Haas oscillations with vanishing resistance at filling factor ν=1. At low B the system undergoes a quantum Hall insulator transition with a dramatic increase of Rxx for all temperatures. The Hall resistance is shown for temperature T=30mK. Inset, Temperature dependence of the zero-field resistance (Ubias=0.5V) at various gate voltages, demonstrating the tunability from strongly to weakly localized with increasing carrier density.

  3. Magnetic-field-driven hole delocalization in the inverted doped structure.
    Figure 3: Magnetic-field-driven hole delocalization in the inverted doped structure.

    af, Two-terminal resistance of the inverted structure—sample A (ad); sample B (e); computed (f). a,b, Magnetoresistance showing temperature-dependent hystereses and abrupt resistance drops for Ubias=0.01V (a) and Ubias=0.5V (b); Rmax=1010 (a) and Rmax=1012 (b) denotes an upper limit of the experimental set-up. c, Magnetoresistance at different carrier densities varied by the top-gate voltage at T=170mK. d, Current–voltage characteristics at T=40mK for selected values of perpendicular magnetic field (sweep direction marked by an arrow) showing highly nonlinear and linear behaviour at low and high magnetic fields, respectively. The inset shows the magnitude of the total magnetic field corresponding to the abrupt resistance decrease, Bjump (black), and the normal component of Bz (red) as a function of the angle between the magnetic-field direction and the film normal at 40mK. e, Minor loops for sample B at 400mK, documenting enhanced relaxation times. Upward B-field sweeps were stopped at B=0.31T. Then, after different waiting times indicated in the figure, the magnetic field was swept down. Open black squares show a full up-sweep (after complete relaxation). f, Computed resistance as a function of the magnetic field at various substrate temperatures for L=0.9mm and Ubias=0.11V for sample A. Positions of resistance jumps are marked by arrows.

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Affiliations

  1. Institute of Experimental and Applied Physics, University of Regensburg, D-93040 Regensburg, Germany

    • Ursula Wurstbauer,
    • Dieter Weiss &
    • Werner Wegscheider
  2. Institute of Applied Physics, University of Hamburg, D-20355 Hamburg, Germany

    • Ursula Wurstbauer
  3. Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02 668 Warszawa, Poland

    • Cezary Śliwa &
    • Tomasz Dietl
  4. Institute of Theoretical Physics, University of Warsaw, ul. Hoża 69, PL 00 681 Warszawa, Poland

    • Tomasz Dietl
  5. Present addresses: Department of Physics, Columbia University, New York, New York 10025, USA (U.W.); Solid State Physics Laboratory, ETH Zurich, Zurich 8093, Switzerland (W.W.)

    • Ursula Wurstbauer &
    • Werner Wegscheider

Contributions

Project planning, W.W., D.W.; structure growth and processing, U.W., W.W.; experiments and data analysis, U.W., W.W., D.W.; theory, C.Ś., T.D.; writing, T.D., U.W., W.W., D.W., C.Ś.

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The authors declare no competing financial interests.

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