Transport Spectroscopy of a Spin-Coherent Dot-Cavity System

Rössler, C.; Oehri, David; Zilberberg, Oded; Blatter, G.; Karalic, Matija; Pijnenburg, Jana; Hofmann, Andrea; Ihn, Thomas; Ensslin, Klaus; Reichl, Christian; Wegscheider, Werner

doi:10.1103/physrevlett.115.166603

Cited by 35 publications

(66 citation statements)

References 23 publications

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“…S6 38 ). For quantitative analysis, it is important to note that our SGM experiment realizes a FP cavity 47 and therefore probes the reflection phase of the QPC. This situation differs from previous experiments on QDs using AB rings 48 which probe the transmission phase of the embedded device.…”

Section: Quantum Point Contactsmentioning

confidence: 99%

Electron Phase Shift at the Zero-Bias Anomaly of Quantum Point Contacts

et al. 2016

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The Kondo effect is the many-body screening of a local spin by a cloud of electrons at very low temperature. It has been proposed as an explanation of the zero-bias anomaly in quantum point contacts where interactions drive a spontaneous charge localization. However, the Kondo origin of this anomaly remains under debate, and additional experimental evidence is necessary. Here we report on the first phase-sensitive measurement of the zero-bias anomaly in quantum point contacts using a scanning gate microscope to create an electronic interferometer. We observe an abrupt shift of the interference fringes by half a period in the bias range of the zero-bias anomaly, a behavior which cannot be reproduced by single-particle models. We instead relate it to the phase shift experienced by electrons scattering off a Kondo system. Our experiment therefore provides new evidence of this many-body effect in quantum point contacts. Quantum point contacts1,2 (QPCs) are small constrictions in high-mobility two-dimensional electron gases (2DEGs) controlled by a metallic split gate at the surface of a semiconductor heterostructure. Despite their apparent simplicity, they reveal complex many-body phenomena which defy our understanding. When these quasione-dimensional ballistic channels are sufficiently open, electrons are perfectly transmitted via each available transverse mode 3 , and the conductance is quantized in units of the conductance quantum 2e 2 /h. Below the first conductance plateau however, this single-particle picture fails due to the increasing importance of many-body effects. An additional shoulder shows up in the linear conductance curve around 0.7 × 2e 2 /h, called the 0.7 anomaly 4 , and a narrow peak of enhanced conductance appears around zero bias in the non-linear conductance curves at low enough temperature, called the zero-bias anomaly 7 (ZBA). The peak behavior versus temperature and magnetic field was shown to share strong similarities with the Kondo effect in quantum dots 6,7 (QDs), i.e. the many-body screening of a local spin by conduction electrons below a characteristic temperature 5,8,9 . However, deviations of the ZBA from the established Kondo effect have been reported [6][7][8]11 , and the occurrence of this effect in QPCs remains a debated issue [14][15][16]

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Section: Quantum Point Contactsmentioning

confidence: 99%

Electron Phase Shift at the Zero-Bias Anomaly of Quantum Point Contacts

et al. 2016

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“…We can visualize our system as consisting of a dynamic electronic cavity [16], which is defined by the arch gate and the reflector (the reflector is required to define the focal point of the cavity). The multiple reflection of emitted 1D electrons between the reflector and the arch gates give rise to a continuum of localized states.…”

Section: Resultsmentioning

confidence: 99%

“…The energy spacing between different cavity states is small (of the order of 100 μeV from Ref. [16]) due to the large size of the cavity. This indicates one 1D state may couple to several cavity states and can result in relatively broad fine oscillations.…”

Section: B Fano Resonancementioning

confidence: 99%

“…Soon after the first observation of quantized conductance in a quasi-one-dimensional (1D) quantum wire [19,20], a number of interesting observations have been made such as the "0.7 structure" [21], incipient Wigner lattice [22,23], coherent electron focusing [24][25][26], etc. Experiments of coupling between a QPC, which provides a stream of collimated 1D electrons, and a waveguide [15] and that between a quantum dot and cavity [16] have been performed, where a pronounced modulation of conductance of the system and changing of Coulomb peaks were observed. Knowledge of the resonant interference effects arising from the coupling of two quantum states is of fundamental significance for the development of technology for quantum-information processing.…”

Section: Introductionmentioning

confidence: 99%

“…Among its various applications, quantum interference has been used successfully as a tool to investigate properties of particles such as monitoring correlation and entanglement as demonstrated in MachZehnder interferometery [7,8], Aharonov-Bohm interferometery [9,10], Hanbury Brown-Twiss interferometery [11,12], and the electronic analogue of the Hong-OuMandel device [13,14]. Among all the striking phenomena, it is particularly interesting to note that quantum interference is extremely suitable for studying coupling between different quantum systems [15][16][17], which is crucial for the design of integrated quantum circuits.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interference Effects in a Tunable Quantum Point Contact Integrated with an Electronic Cavity

et al. 2017

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We show experimentally how quantum interference can be produced using an integrated quantum system comprising an arch-shaped short quantum wire (or quantum point contact, QPC) of 1D electrons and a reflector forming an electronic cavity. On tuning the coupling between the QPC and the electronic cavity, fine oscillations are observed when the arch QPC is operated in the quasi-1D regime. These oscillations correspond to interference between the 1D states and a state which is similar to the Fabry-Perot state and suppressed by a small transverse magnetic field of AE60 mT. Tuning the reflector, we find a peak in resistance which follows the behavior expected for a Fano resonance. We suggest that this is an interesting example of a Fano resonance in an open system which corresponds to interference at or near the Ohmic contacts due to a directly propagating, reflected discrete path and the continuum states of the cavity corresponding to multiple scattering. Remarkably, the Fano factor shows an oscillatory behavior taking peaks for each fine oscillation, thus, confirming coupling between the discrete and continuum states. The results indicate that such a simple quantum device can be used as building blocks to create more complex integrated quantum circuits for possible applications ranging from quantum-information processing to realizing the fundamentals of complex quantum systems.

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Auger-spectroscopy in quantum Hall edge channels and the missing energy problem

et al. 2019

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Quantum Hall edge channels offer an efficient and controllable platform to study quantum transport in one dimension. Such channels are a prospective tool for the efficient transfer of quantum information at the nanoscale, and play a vital role in exposing intriguing physics. Electric current along the edge carries energy and heat leading to inelastic scattering, which may impede coherent transport. Several experiments attempting to probe the concomitant energy redistribution along the edge reported energy loss via unknown mechanisms of inelastic scattering. Here we employ quantum dots to inject and extract electrons at specific energies, to spectrally analyse inelastic scattering inside quantum Hall edge channels. We show that the missing energy puzzle could be untangled by incorporating non-local Auger-like processes, in which energy is redistributed between spatially separate parts of the sample. Our theoretical analysis, accounting for the experimental results, challenges common-wisdom analyses which ignore such non-local decay channels.

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Transport Spectroscopy of a Spin-Coherent Dot-Cavity System

Cited by 35 publications

References 23 publications

Electron Phase Shift at the Zero-Bias Anomaly of Quantum Point Contacts

Electron Phase Shift at the Zero-Bias Anomaly of Quantum Point Contacts

Interference Effects in a Tunable Quantum Point Contact Integrated with an Electronic Cavity

Auger-spectroscopy in quantum Hall edge channels and the missing energy problem

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