A multipurpose torsional magnetometer with optical detection

Schaapman, M.R.; Christianen, P.C.M.; Maan, J. C.; Reuter, D.; Wieck, A. D.

doi:10.1063/1.1498152

Cited by 23 publications

(22 citation statements)

References 14 publications

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“…A plastic disc was mounted on the fibre with its face perpendicular to the fibre. On one side of the disc a semicircular capacitance electrode was evaporated, and electrically Schematic diagrams of the magnetometers of: (a) Eisenstein et al [6]; (b) Templeton [10]; (c) Wiegers et al [11]; (d) Matthews et al [12]; (e) Schaapman et al [13]; (f) Schwarz et al [14]. The magnetic field direction in (a) and (c) to (f) is vertical; in (b) it is horizontal.…”

Section: Torsion-balance Magnetometersmentioning

confidence: 99%

Magnetometry of low-dimensional electron and hole systems

Usher¹,

Elliott²

2009

J. Phys.: Condens. Matter

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Abstract. The high magnetic field, low-temperature magnetic properties of lowdimensional electron and hole systems reveal a wealth of fundamental information. Quantum oscillations of the thermodynamic equilibrium magnetization yield the total density of states, a central quantity in understanding the quantum Hall effect in 2D systems. The magnetization arising from non-equilibrium circulating currents reveals details, not accessible with traditional measurements, of the vanishingly small longitudinal resistance in the quantum Hall regime. We review how the technique of magnetometry has been applied to these systems, the most important discoveries that have been made, and their theoretical significance.

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Section: Torsion-balance Magnetometersmentioning

confidence: 99%

Magnetometry of low-dimensional electron and hole systems

Usher¹,

Elliott²

2009

J. Phys.: Condens. Matter

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“…Most importantly, the shape of these nanostructures differs considerably from that of ideal rings in two respects: (i) the presence of indium in their center resulting in the absence of a hole in the nanostructures and (ii) a distinct anisotropy of the nanostructure, i.e., the height of the rim is larger in the [110] than in the 1 10 direction [10,17]. The magnetic moment of the nanostructures is obtained from magnetization experiments using a torque magnetometer [18]. These measurements were performed at temperatures of T 1:2 K and T 4:2 K in magnetic fields up to 15 T. The total magnetization of the sample is due to about 1: 5 10 11 nanostructures with a total number of electrons N 2: 2 10 11 .…”

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confidence: 99%

Oscillatory Persistent Currents in Self-Assembled Quantum Rings

et al. 2007

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We report the direct measurement of the persistent current carried by a single electron by means of magnetization experiments on self-assembled InAs=GaAs quantum rings. We measured the first Aharonov-Bohm oscillation at a field of 14 T, in perfect agreement with our model based on the structural properties determined by cross-sectional scanning tunneling microscopy measurements. The observed oscillation magnitude of the magnetic moment per electron is remarkably large for the topology of our nanostructures, which are singly connected and exhibit a pronounced shape asymmetry. DOI: 10.1103/PhysRevLett.99.146808 PACS numbers: 73.21.La, 73.23.Ra, 78.67.Hc In quantum mechanics, particular attention is paid to phenomena occurring due to the phase coherence of charge carriers in doubly connected (ring) topologies. Electrons confined to a submicron ring manifest a topologically determined quantum-interference phenomenon, known as the Aharonov-Bohm (AB) effect [1], as a result of the oscillatory behavior of their energy levels as a function of an applied magnetic field. This behavior is usually associated with the occurrence of oscillatory persistent currents in the ring [2 -4]. Experimental evidence for AB oscillations has been detected in the mesoscopic regime in metallic [5,6] and semiconducting [7,8] rings, containing many electrons. We address the occurrence of the AB effect in defect-free self-assembled semiconductor nanostructures [9][10][11][12][13]. The ability to fill nanostructures with only a few (1-2) electrons offers the unique possibility to detect magnetic field induced oscillations in the persistent current carried by single electron states. We report the first direct measurement by means of ultrasensitive magnetization experiments of the oscillatory persistent current carried by a single electron in self-assembled InAs/GaAs ''volcanolike'' nanostructures. Remarkably, this single electron current occurs even in the absence of an opening [14] in our nanostructures, which is required for the AB effect in the standard treatment [1]. The magnetic field at which the first oscillation in the magnetic moment arises is much higher than expected from the diameter of the quantum rings as determined by atomic force microscopy [13]. However, the experiments are in good agreement with a model based on the structural parameters as determined with cross-sectional scanning tunneling microscopy (XSTM) measurements.The persistent current was determined via the magnetic moment of electrons in a highly homogeneous ensemble of InAs self-assembled nanostructures. The sample was grown by molecular beam epitaxy and contains 29 mutually decoupled periods [ Fig. 1(a)] [15]. Each period consists of a nanostructured InAs layer, between two 24 nm GaAs layers, and a 2 nm doped (7 10 16 cm ÿ3 Si) GaAs layer that provides electrons to the InAs nanostructures. We used a one-dimensional Poisson solver [16] to estimate the average number of electrons per nanostructure to be about 1.5. Considering the two possible spin orientations we ...

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“…A smooth magnetic background has been removed from the raw data by subtracting a low-order polynomial fit in 1 / B. 10,25,26 We find a sawtoothlike dHvA signal whose sharply dropping slopes coincide with the integer filling factors. The peak-to-peak amplitude at filling factor = 2 in panel ͑a͒ amounts to ⌬M =2 = 3.6ϫ 10 −14 J / T, one order of magnitude smaller than in Si/SiGe.…”

Section: Resultsmentioning

confidence: 99%

“…6, there have been important developments to improve the resolution of dHvA studies. 7 Improvements were achieved by either sophisticated torque magnetometers using torsion balance along a thin wire [8][9][10] or a specially designed superconducting quantum interference device ͑SQUID͒ at 300 mK using very low-noise SQUID electronics. 11,12 These approaches provided a high sensitivity but did not allow to study the dHvA effect under a large tilt angle.…”

Section: Introductionmentioning

confidence: 99%

De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

et al. 2009

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We report highly sensitive de Haas-van Alphen ͑dHvA͒ effect measurements on a high-mobility twodimensional electron system in an AlAs quantum well. Here two valleys are occupied forming a pseudospin system. At 400 mK, the dHvA effect shows pronounced oscillations at filling factors = 1 to four. In the quantum limit at = 1 the data are consistent with an interaction-enhanced valley splitting, which exceeds the Zeeman spin splitting in a perpendicular field B. When tilting B the energy gap ⌬E at = 1 shows first an unexpectedly strong angular dependence and then remains constant. This suggests a crossover in the energy gap, most likely from a spin to a pseudospin gap. We attribute the strong initial dependence of ⌬E on the tilt angle to skyrmion-type spin excitations. Surprisingly, the dHvA oscillation amplitudes do not display coincidence phenomena at higher filling factors. This is explained by the large valley splitting and avoided crossings of energy levels.

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A multipurpose torsional magnetometer with optical detection

Cited by 23 publications

References 14 publications

Magnetometry of low-dimensional electron and hole systems

Magnetometry of low-dimensional electron and hole systems

Oscillatory Persistent Currents in Self-Assembled Quantum Rings

De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

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