Sikorski and Merkt reply

Sikorski, Ch.; Merkt, U.

doi:10.1103/physrevlett.64.3101

Cited by 17 publications

(18 citation statements)

References 4 publications

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“…The resonances summarized in Fig. 2(b) differ quite strongly from those observed in quantum dots [14,17], where in general, only two resonances are observed, one of which increases with increasing field, whereas the other decreases. On the other hand, Fig.…”

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confidence: 64%

Spectroscopy of Nanoscopic Semiconductor Rings

et al. 2000

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Making use of self-assembly techniques, we realize nanoscopic semiconductor quantum rings in which the electronic states are in the true quantum limit. We employ two complementary spectroscopic techniques to investigate both the ground states and the excitations of these rings. Applying a magnetic field perpendicular to the plane of the rings, we find that, when approximately one flux quantum threads the interior of each ring, a change in the ground state from angular momentum ᐉ 0 to ᐉ 21 takes place. This ground state transition is revealed both by a drastic modification of the excitation spectrum and by a change in the magnetic-field dispersion of the single-electron charging energy. PACS numbers: 73.20.Dx, 03.65.Bz, 78.66.Fd The fascination of ringlike atomic and quantum structures dates back to Kekulé's famous proposal of the structure of benzene [1]. Particularly interesting are the magnetic properties of such nonsimply connected quantum systems, which are related to the possibility of trapping magnetic flux in their interior. Trapping of a single flux quantum in a small molecule such as benzene is impossible with the magnetic fields available in today's laboratories. In recent years, however, the availability of submicron solid-state ring structures has triggered a strong interest in the magnetic properties of rings, especially in view of the fact that, even in the presence of scattering, the many-particle ground state becomes chiral in a magnetic field, which leads to so-called "persistent currents" [2]. The large body of theoretical work on the properties of quantum rings [3] is accompanied by a number of ground breaking experimental investigations of the magnetic and transport properties of rings [4]. These studies have been carried out in the mesoscopic range, where scattering still influences the phase coherent transport, and a large number of quantum states are filled. To the best of our knowledge, no spectroscopic data is available on rings in the scatter-free, few-electron quantum limit. Furthermore, despite a strong theoretical interest [5,6], the only data available on the excitations of rings were taken on macroscopic structures [7].Here, we report on the spectroscopy of the ground states and excitations of self-assembled, nanoscopic InGaAs quantum rings, occupied with one or two electrons each, and subjected to magnetic fields 0 # B # 12 T, corresponding to 0-1.5 flux quanta threading the interior of the ring. In both ground state and excitation spectroscopies we observe characteristic changes at about B 8 T which are attributed to the development of a magneticfield-induced chiral ground state.The quantum rings are fabricated by solid-source molecular-beam epitaxy, using the Stranski-Krastanov growth mode, which has now become a well-established technique for the fabrication of high-quality, selfassembled semiconductor nanostructures [8]. Recently, we reported on a remarkable change in morphology when InAs self-assembled dots, grown on GaAs, are covered with a thin layer of GaAs and annealed...

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confidence: 64%

Spectroscopy of Nanoscopic Semiconductor Rings

et al. 2000

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“…The theorem states that only the center-of-mass (CM) degree of freedom couples to a spatially homogenous electromagnetic field. In previous studies of excitations in quantum dots by coupling radiation via antennas only CM excitations were found [11,19,20]. Here we 'move' the radiation source close to the quantum dots, in an attempt to verify whether the inhomogeneity of the near-field radiation affects the electronic excitations.…”

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confidence: 93%

“…In contrast to the excitation spectrum of real atoms or molecules, the spectrum of single or even coupled quantum dots reveals a striking difference in the discrete level structure. For quantum dots it has been shown in a whole variety of experiments that Kohn's theorem [17] prevails [18,19]. The theorem states that only the center-of-mass (CM) degree of freedom couples to a spatially homogenous electromagnetic field.…”

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confidence: 99%

Microwave spectroscopy on a double quantum dot with an on-chip Josephson oscillator

Holleitner

Qin²,

Simmel³

et al. 2000

New J. Phys.

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We present measurements on microwave spectroscopy on a double quantum dot with an on-chip microwave source. The quantum dots are realized in the two-dimensional electron gas of an AlGaAs/GaAs heterostructure and are weakly coupled in series by a tunneling barrier forming an 'ionic' molecular state. As a microwave source we employ a Josephson oscillator formed by a long Nb/Al-AlO x /Nb junction. We find photon assisted tunneling sidebands induced by the Josephson oscillator and compare the results with those using an externally operated microwave source. 07.57Hm;73.40Gk;85.30.Vw Typeset using REVT E X

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“…Since the very first demonstration of feasibility of observation of speckles by coherent hard X-rays (Sutton et al, 1991), XPCS has been successfully applied to study a wide range of systems encompassing both soft and hard matter. The studies so far have covered diverse systems, such as colloidal suspensions Sikorski et al, 2011a), gels (Bandyopadhyay et al, 2004;Madsen et al, 2010), liquid crystals (Sikharulidze et al, 2002), polymers (Kim et al, 2003;Jiang et al, 2007), liquid surfaces (Madsen et al, 2004) and hard materials (Fluerasu et al, 2005;Ruta et al, 2014). A variant of the technique, termed X-ray speckle visibility spectroscopy, has also been employed for the measurement of dynamics.…”

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confidence: 99%

Distributed X-ray photon correlation spectroscopy data reduction using Hadoop MapReduce

Khan

Narayanan

Sersted

et al. 2018

J Synchrotron Radiat

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Multi-speckle X-ray photon correlation spectroscopy (XPCS) is a powerful technique for characterizing the dynamic nature of complex materials over a range of time scales. XPCS has been successfully applied to study a wide range of systems. Recent developments in higher-frame-rate detectors, while aiding in the study of faster dynamical processes, creates large amounts of data that require parallel computational techniques to process in near real-time. Here, an implementation of the multi-tau and two-time autocorrelation algorithms using the Hadoop MapReduce framework for distributed computing is presented. The system scales well with regard to the increase in the data size, and has been serving the users of beamline 8-ID-I at the Advanced Photon Source for near real-time autocorrelations for the past five years.

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Sikorski and Merkt reply

Cited by 17 publications

References 4 publications

Spectroscopy of Nanoscopic Semiconductor Rings

Spectroscopy of Nanoscopic Semiconductor Rings

Microwave spectroscopy on a double quantum dot with an on-chip Josephson oscillator

Distributed X-ray photon correlation spectroscopy data reduction using Hadoop MapReduce

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