Scanning-gate-induced effects in nonlinear transport through nanostructures

Gorini, Cosimo; Weinmann, Dietmar; Jalabert, Rodolfo A.

doi:10.1103/physrevb.89.115414

Cited by 8 publications

(12 citation statements)

References 42 publications

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“…When the QPC is tuned to the first plateau ( Fig. 4(a), top panel), the fringes evolve monotonically with source-drain bias due to a change in wavelength for electrons injected at higher energy 44 , and the extracted phase is linear (blue curve, bottom panel). Below the first plateau (second panel), the fringes exhibit a sharp phase jump at negative bias and a smooth one at positive bias, also visible on the extracted phase (red curve, bottom panel).…”

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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“…This symmetry implies that all even terms of the expansion (34) vanish, and in particular g 2 = 0. The presence of an SGM tip breaks the left-right symmetry of the system and thereby leads to a nite g 2 and a rectication eect induced by the tip [14]. The perturbative treatment in second order of the tip strength applicable to the regime of conductance quantization already shows this eect yielding a characteristic signature that can be observed in experiments.…”

Section: Beyond Linear Response In the Bias Voltagementioning

confidence: 88%

“…Markus Büttiker was again a key player in developing the theory of non-linear transport [23,24], stressing the importance of working with formulations that are gauge-invariant with respect to a general boost of the single-particle energies of the problem. We have used this important understanding to work out the perturbative eect of the SGM tip on the higher order terms [14] in the current-voltage relation…”

Section: Beyond Linear Response In the Bias Voltagementioning

confidence: 99%

“…The perturbative approach previously described applies to the cases of very weak tip voltages or a tip suciently far away from the QPC in order to have a very small matrix element (14) of the perturbation. While experimental data with weak tips exist in some cases [25], most of the experimental work [2,3,5] has been done with tip voltages strong enough to create a divot of depletion in the two-dimensional electron gas, leading to a regime where perturbation theory is not applicable.…”

Section: Conductance Corrections Due To a Hard-wall Tip In The Clean mentioning

confidence: 99%

“…The linearresponse regime of small bias voltages [11,13], as well as the weakly non-linear case [14] are presented. In an attempt to connect with other theoretical and experimental work, we go beyond the perturbative regime and study SGM setups by means of semi-classical approximations and numerical calculations.…”

Section: Introductionmentioning

confidence: 99%

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