Transmission Phase in the Kondo Regime Revealed in a Two-Path Interferometer

Takada, Shintaro; Bäuerle, Christopher; Yamamoto, Mahito; Watanabe, Kenta; Hermelin, Sylvain; Meunier, Tristan; Alex, Arne; Weichselbaum, Andreas; Delft, Jan von; Ludwig, Arne; Wieck, A. D.; Tarucha, Seigo

doi:10.1103/physrevlett.113.126601

Cited by 47 publications

(60 citation statements)

References 35 publications

(22 reference statements)

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“…Further experiments claimed to have observed the π/2 phase shift corresponding to the Kondo regime but the temperature of this experiments was much higher than the Kondo temperature and outside the regime where the Kondo result is expected to hold [10]. More recent experiments by Takada et al have managed to measure the transmission phase shift through a Kondo correlated quantum dot and find the transition between the Kondo regime and Coulomb blockade regime with excellent agreement with Numerical Renormalization Group calculations [11]. Effects of the ratio between width and interaction strength have also been experimentally investigated [12].…”

Section: Introductionmentioning

confidence: 67%

Time-dependent wave packet simulations of transport through Aharanov–Bohm rings with an embedded quantum dot

Kreisbeck¹,

Kramer²,

Molina³

2017

J. Phys.: Condens. Matter

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Abstract. We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin-Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations.

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Section: Introductionmentioning

confidence: 67%

Time-dependent wave packet simulations of transport through Aharanov–Bohm rings with an embedded quantum dot

Kreisbeck¹,

Kramer²,

Molina³

2017

J. Phys.: Condens. Matter

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“…It can be tuned into a two-path interferometer in the weak tunnel-coupling regime when the two output currents through the two coupled wires oscillate with magnetic field but opposite phase [20][21][22] . We have used this original device to investigate the transmission phase shift across a Kondo correlated QD and obtained a very good agreement for the phase shift between experiment and theory by carefully analyzing the anti-phase oscillations 23 . In addition we have noticed that a smooth phase shift as a function of gate voltage can be observed even when the contributions from other than the direct two-paths exist.…”

mentioning

confidence: 88%

Measurement of the transmission phase of an electron in a quantum two-path interferometer

Takada

Yamamoto

Bäuerle

et al. 2015

Applied Physics Letters

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A quantum two-path interferometer allows for direct measurement of the transmission phase shift of an electron, providing useful information on coherent scattering problems. In mesoscopic systems, however, the two-path interference is easily smeared by contributions from other paths, and this makes it difficult to observe the true transmission phase shift. To eliminate this problem, multi-terminal Aharonov-Bohm (AB) interferometers have been used to derive the phase shift by assuming that the relative phase shift of the electrons between the two paths is simply obtained when a smooth shift of the AB oscillations is observed. Nevertheless the phase shifts using such a criterion have sometimes been inconsistent with theory. On the other hand, we have used an AB ring contacted to tunnel-coupled wires and acquired the phase shift consistent with theory when the two output currents through the coupled wires oscillate with well-defined anti-phase. Here, we investigate thoroughly these two criteria used to ensure a reliable phase measurement, the anti-phase relation of the two output currents and the smooth phase shift in the AB oscillation. We confirm that the well-defined anti-phase relation ensures a correct phase measurement with a quantum two-path interference. In contrast we find that even in a situation where the anti-phase relation is less well-defined, the smooth phase shift in the AB oscillation can still occur but does not give the correct transmission phase due to contributions from multiple paths. This indicates that the phase relation of the two output currents in our interferometer gives a good criterion for the measurement of the true transmission phase while the smooth phase shift in the AB oscillation itself does not.The transmission phase of an electron plays a crucial role in various quantum interference phenomena. Full characterization of the coherent transport therefore requires a reliable phase measurement, but this is still challenging. One may envisage a quantum two-path interferometer because the interference is measured as a function of the phase difference between the two paths. For instance the phase shift across a quantum dot (QD), in which one can control the quantum state of single electrons, can be measured using a QD embedded in one of the two arms of the interferometer. The theory predicts a Breit-Wigner type phase shift across a Coulomb peak (CP) 1 and a π/2 phase shift across a Kondo-singlet state 2 and both were experimentally investigated. The Breit-Wigner type phase shift was confirmed by a pioneering experiment for a QD embedded in a multiterminal Aharonov-Bohm (AB) interferometer 3 . The phase shift was derived from a smooth shift of AB oscillation phase. However, unanticipated results have sometimes been observed, such as a universal phase lapse between CPs for a large QD 3,4 and a large phase shift exceeding π across two Coulomb peaks of a spin degenerated level for a Kondo correlated QD 5,6 . Although a) Electronic mail: shintaro.takada@neel.cnrs.fr several mechanisms have b...

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“…This screening produces a narrow resonance in the density of states at the Fermi level and gives rise to a conductance peak at zero bias 50 . Below the Kondo temperature, the transmission phase of a symmetric QD equals π/2 in the gate voltage range of a Kondo valley [28][29][30] , and the conductance reaches 2e 2 /h 3,51 . The phase shift observed in our experiment at zero bias may correspond to this Kondo scattering phase, but in the reflection coefficient, which can be twice the value of the transmission coefficient 15 .…”

Section: Quantum Point Contactsmentioning

confidence: 99%

“…Recently, a phase measurement on a QPC has been reported 26 , but no significant deviation from the single-particle prediction has been found 27 . In the past, the transmission phase of QDs in the Kondo regime was measured by embedding them in Aharonov-Bohm (AB) [28][29][30] . Here we measure instead the reflection phase of the system and observe a phase shift by π of the interference fringes in the bias voltage range of the ZBA.…”

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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Transmission Phase in the Kondo Regime Revealed in a Two-Path Interferometer

Cited by 47 publications

References 35 publications

Time-dependent wave packet simulations of transport through Aharanov–Bohm rings with an embedded quantum dot

Time-dependent wave packet simulations of transport through Aharanov–Bohm rings with an embedded quantum dot

Measurement of the transmission phase of an electron in a quantum two-path interferometer

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

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