Observation of the Local Structure of Landau Bands in a Disordered Conductor

Schmidt, Thomas A.; Haug, Rolf J.; Klitzing, K. von; Förster, A.; Lüth, H.

doi:10.1103/physrevlett.78.1540

Cited by 41 publications

(32 citation statements)

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“…Such impurity states with an energy lower than the quantum well in between the barriers most likely stem from unintended donor atoms within the well. [11][12][13][14] The I-Vcurve is slightly asymmetric regarding both bias polarities. We attribute this to the different transmission coefficients of both tunneling barriers due to their differing growth thicknesses.…”

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“…Under certain bias conditions the tunneling current through our sample flows through a single zero-dimensional state. 13,14 Therefore we are dealing with 3d-0d-3d tunneling in contrast to the above-mentioned experimental studies where the tunneling takes place through a two-dimensional subband (3d-2d-3d). 5,6 Our sample consists of a nearly symmetric double-barrier resonant-tunneling structure grown by molecular-beam epitaxy on a n ϩ -type GaAs substrate ͓see Fig.…”

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confidence: 99%

“…This is caused by the diamagnetic shift of the resonant state E S . This allows us to estimate the classical diameter 13 of the zero-dimensional state to rϳ10 nm. Additionally, the I-V-curve does reveal a second weak structure which is marked with ''Y '' in Fig.…”

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Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum

et al. 2004

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We investigate the noise properties of a GaAs /Al x Ga 1Ϫx As resonant-tunneling structure at bias voltages where the current characteristic is determined by single electron tunneling. We discuss the suppression of the shot noise in the framework of a coupled two-state system. For large bias voltages we observe superPoissonian shot noise up to values of the Fano factor ␣Ϸ10. DOI: 10.1103/PhysRevB.69.113316 PACS number͑s͒: 73.63.Kv, 73.40.Gk, 72.70.ϩm Shot noise allows for a direct measurement of the correlation in a current of discrete charges. In the case of a totally uncorrelated current, one observes the so-called full or Poissonian shot noise. 1 The corresponding noise power S displays a linear dependence Sϭ2eI on the stationary current I as long as the applied bias voltage V SD is large compared to the thermal energy: eV SD ӷ2k B T. 2 Full current shot noise arises, e.g., in a single tunneling barrier, since the tunneling process of different electrons are independent of each other.However, if an additional source of negative correlation is introduced the noise amplitude was shown to be reduced. 3,4 For resonant tunneling through a double-barrier structure this is attributed to the dependency of successive tunneling events caused by the finite dwell time of the resonant state. 5,6 This suppression of the shot noise has also been observed for resonant tunneling through zero-dimensional systems. 7,8 For the opposite case of a positive correlation between individual tunneling events the noise power can even become super-Poissonian. 9,10 We report on noise measurements of a resonant-tunneling double-barrier structure. Under certain bias conditions the tunneling current through our sample flows through a single zero-dimensional state. 13,14 Therefore we are dealing with 3d-0d-3d tunneling in contrast to the above-mentioned experimental studies where the tunneling takes place through a two-dimensional subband (3d-2d-3d). 5,6 Our sample consists of a nearly symmetric double-barrier resonant-tunneling structure grown by molecular-beam epitaxy on a n ϩ -type GaAs substrate ͓see Fig. 1͑a͔͒. The heterostructure is formed by a 10-nm-wide GaAs quantum well sandwiched between two Al 0.3 Ga 0.7 As-tunneling barriers of 5 and 6 nm thickness. The contacts consist of 300-nm-thick GaAs layers doped with Si (4ϫ10 17 cm Ϫ3 ) and they are separated from the active region by a 7 nm thick undoped GaAs spacer layer. The geometrical diameter of the diode is 1 m.The current-voltage (I-V) characteristic is plotted in Fig. 1͑c͒. The upper inset shows the characteristic shape of the resonance due to tunneling through the two-dimensional subband at V SD ϭϮ130 mV. However, we concentrate our measurements on small bias voltages ͉V SD ͉р10 mV, where we find a pronounced current step ͑marked with ''X''͒. This feature indicates the presence of at least one single impurity in the nominally undoped GaAs, as depicted schematically in Fig. 1͑b͒. Such impurity states with an energy lower than the quantum well in between the barriers most like...

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Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum

et al. 2004

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“…In the tunneling-spectroscopy experiments [21,22,10,11,23,24,[12][13][14] the measured quantity is a resonant-tunneling current, I sd , through a localized impurity state as a function of the source-drain bias, V sd . Such an impurity plays the role of a "spectrometer" since its energy position, ǫ 0 , changes with V sd .…”

Section: Manifestation In the Tunneling Spectroscopymentioning

confidence: 99%

“…This fact was recently utilized in the resonant-tunneling spectroscopy [10][11][12][13][14] of the LDOS. More specifically, the correlator of the LDOS determines the behavior of correlation function, C(δV ), of the fluctuations of the tunneling conductance with the change, δV , of the source-drain bias.…”

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Spin-orbit-induced correlations of the local density of states in a two-dimensional electron gas

2006

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We study the local density of states (LDOS) of two-dimensional electrons in the presence of spin-orbit (SO) coupling. Although SO coupling has no effect on the average density of states, it manifests itself in the correlations of the LDOS. Namely, the correlation function acquires two satellites centered at energy difference equal to the SO splitting, 2ωSO, of the electron Fermi surface. For a smooth disorder the satellites are well separated from the main peak. Weak Zeeman splitting ωZ ≪ ωSO in a parallel magnetic field causes an anomaly in the shape of the satellites. We consider the effect of SO-induced satellites in the LDOS correlations on the shape of the correlation function of resonant-tunneling conductances at different source-drain biases, which can be measured experimentally. This shape is strongly sensitive to the relation between ωSO and ωZ.

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Resonant Tunneling Through an Impurity Level: A Probe of Coherent States in a Disordered Metal

Schmidt

König

Haug

et al. 2001

Kondo Effect and Dephasing in Low-Dimensional Metallic Systems

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Observation of the Local Structure of Landau Bands in a Disordered Conductor

Cited by 41 publications

References 14 publications

Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum

Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum

Spin-orbit-induced correlations of the local density of states in a two-dimensional electron gas

Resonant Tunneling Through an Impurity Level: A Probe of Coherent States in a Disordered Metal

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