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Angle-dependent magnetotransport in GaAs/InAs core/shell nanowires.

Haas F, Wenz T, Zellekens P, Demarina N, Rieger T, Lepsa M, Grützmacher D, Lüth H, Schäpers T - Sci Rep (2016)

Bottom Line: These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell.Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles.We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation.

View Article: PubMed Central - PubMed

Affiliation: Peter Grünberg Institute 9, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.

ABSTRACT
We study the impact of the direction of magnetic flux on the electron motion in GaAs/InAs core/shell nanowires. At small tilt angles, when the magnetic field is aligned nearly parallel to the nanowire axis, we observe Aharonov-Bohm type h/e flux periodic magnetoconductance oscillations. These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell. With increasing tilt of the nanowire in the magnetic field, the flux periodic magnetoconductance oscillations disappear. Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles. We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation.

No MeSH data available.


Related in: MedlinePlus

(a) Normalized and smoothed Fourier transformation amplitudes of the differentiated magnetoconductance measurements of Fig. 3. Three profile cuts for γA = 15°, 47° and 90° are given in (b). The dotted box for γ ≤ 31° marks the expected frequency range for an electron enclosing magnetic flux quanta Φ0 = h/e while moving on the very outermost or innermost perimeter of the InAs shell. The illustrations in (c) show potential closed electron paths, either caused by the nanowire core/shell geometry or by defect scattering, which each enclose magnetic flux Φ at different magnetic field alignments. The former results in Aharonov–Bohm type magnetoconductance oscillations, the latter in UCF. The size and multitude of such closed loops determines the main components of the Fourier amplitudes. With increasing tilt the background UCF become the most prominent feature of the spectrum, highlighted by a dotted guideline.
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f4: (a) Normalized and smoothed Fourier transformation amplitudes of the differentiated magnetoconductance measurements of Fig. 3. Three profile cuts for γA = 15°, 47° and 90° are given in (b). The dotted box for γ ≤ 31° marks the expected frequency range for an electron enclosing magnetic flux quanta Φ0 = h/e while moving on the very outermost or innermost perimeter of the InAs shell. The illustrations in (c) show potential closed electron paths, either caused by the nanowire core/shell geometry or by defect scattering, which each enclose magnetic flux Φ at different magnetic field alignments. The former results in Aharonov–Bohm type magnetoconductance oscillations, the latter in UCF. The size and multitude of such closed loops determines the main components of the Fourier amplitudes. With increasing tilt the background UCF become the most prominent feature of the spectrum, highlighted by a dotted guideline.

Mentions: At lowest angles γA ≤ 31° we observe clearly visible periodic magnetoconductance oscillations with an average period of ΔBA = 170(3) mT over the full range of magnetic fields on top of a slowly varying background. Additional measurements on sample A as well as on sample B have shown, that these periodic oscillations prevail up to 14 T without notable decrease in amplitude at high magnetic fields. By differentiating the data with respect to the magnetic field B, we calculate the corresponding Fourier transformation (FT) of the measurement without the constant conductance offset and focus on the low and high frequency components of the signal. The results for all measurements made on sample A are shown in Fig. 4 (see Fig. S2 in the supplementary information for sample B). The results were normalized to compare the main frequency contributions between all tilt angles. At lowest angles γA ≤ 31°, we observe two distinct frequency components with nonzero contribution to the Fourier spectrum, one reaching from f = 0 to 3.0 T−1 and the second ranging around a clear peak at a frequency of about f = 6.0 T−1 (marked by the dotted box in Fig. 4(a)).


Angle-dependent magnetotransport in GaAs/InAs core/shell nanowires.

Haas F, Wenz T, Zellekens P, Demarina N, Rieger T, Lepsa M, Grützmacher D, Lüth H, Schäpers T - Sci Rep (2016)

(a) Normalized and smoothed Fourier transformation amplitudes of the differentiated magnetoconductance measurements of Fig. 3. Three profile cuts for γA = 15°, 47° and 90° are given in (b). The dotted box for γ ≤ 31° marks the expected frequency range for an electron enclosing magnetic flux quanta Φ0 = h/e while moving on the very outermost or innermost perimeter of the InAs shell. The illustrations in (c) show potential closed electron paths, either caused by the nanowire core/shell geometry or by defect scattering, which each enclose magnetic flux Φ at different magnetic field alignments. The former results in Aharonov–Bohm type magnetoconductance oscillations, the latter in UCF. The size and multitude of such closed loops determines the main components of the Fourier amplitudes. With increasing tilt the background UCF become the most prominent feature of the spectrum, highlighted by a dotted guideline.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835758&req=5

f4: (a) Normalized and smoothed Fourier transformation amplitudes of the differentiated magnetoconductance measurements of Fig. 3. Three profile cuts for γA = 15°, 47° and 90° are given in (b). The dotted box for γ ≤ 31° marks the expected frequency range for an electron enclosing magnetic flux quanta Φ0 = h/e while moving on the very outermost or innermost perimeter of the InAs shell. The illustrations in (c) show potential closed electron paths, either caused by the nanowire core/shell geometry or by defect scattering, which each enclose magnetic flux Φ at different magnetic field alignments. The former results in Aharonov–Bohm type magnetoconductance oscillations, the latter in UCF. The size and multitude of such closed loops determines the main components of the Fourier amplitudes. With increasing tilt the background UCF become the most prominent feature of the spectrum, highlighted by a dotted guideline.
Mentions: At lowest angles γA ≤ 31° we observe clearly visible periodic magnetoconductance oscillations with an average period of ΔBA = 170(3) mT over the full range of magnetic fields on top of a slowly varying background. Additional measurements on sample A as well as on sample B have shown, that these periodic oscillations prevail up to 14 T without notable decrease in amplitude at high magnetic fields. By differentiating the data with respect to the magnetic field B, we calculate the corresponding Fourier transformation (FT) of the measurement without the constant conductance offset and focus on the low and high frequency components of the signal. The results for all measurements made on sample A are shown in Fig. 4 (see Fig. S2 in the supplementary information for sample B). The results were normalized to compare the main frequency contributions between all tilt angles. At lowest angles γA ≤ 31°, we observe two distinct frequency components with nonzero contribution to the Fourier spectrum, one reaching from f = 0 to 3.0 T−1 and the second ranging around a clear peak at a frequency of about f = 6.0 T−1 (marked by the dotted box in Fig. 4(a)).

Bottom Line: These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell.Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles.We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation.

View Article: PubMed Central - PubMed

Affiliation: Peter Grünberg Institute 9, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.

ABSTRACT
We study the impact of the direction of magnetic flux on the electron motion in GaAs/InAs core/shell nanowires. At small tilt angles, when the magnetic field is aligned nearly parallel to the nanowire axis, we observe Aharonov-Bohm type h/e flux periodic magnetoconductance oscillations. These are attributed to transport via angular momentum states, formed by electron waves within the InAs shell. With increasing tilt of the nanowire in the magnetic field, the flux periodic magnetoconductance oscillations disappear. Universal conductance fluctuations are observed for all tilt angles, however with increasing amplitudes for large tilt angles. We record this evolution of the electron propagation from a circling motion around the core to a diffusive transport through scattering loops and give explanations for the observed different transport regimes separated by the magnetic field orientation.

No MeSH data available.


Related in: MedlinePlus