S. Ludwig; "The Role of Phonons for the Back-Action of a Quantum-point-Contact Charge Detector", Sept. 15, 11:00, FENS 2019
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  • S. Ludwig; "The Role of Phonons for the Back-Action of a Quantum-point-Contact Charge Detector", Sept. 15, 11:00, FENS 2019

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Faculty of Engineering and Natural Sciences

 

                             

 SEMINAR ANNOUNCEMENT

 

 

 

The role of phonons for the back–action of a quantum–point–contact charge detector

 

 

S. Ludwig

 

Center for NanoScience and Fakultät für Physik, Ludwig-Maximilians-Universität,

 

Geschwister-Scholl-Platz 1, 80539 München, Germany

 

 

Interactions between nanoscale devices are a key component for solid–state based quantum information processing. For instance the capacitive coupling between a biased quantum point contact (QPC) and quantum dots (QD) is utilized for charge detection of a qubit. In this context, the back–action of a QPC is often associated with direct Coulomb forces between fluctuating charges at the QPC and electrons in the QD [1,2]. On the other hand a driven QPC emits energy, e. g. in the form of phonons. In this talk I will discuss possible back–action mechanisms and present measurements that prove that back–action in a solid state environment can be mediated by phonons.

 

 

We have established a technique to make back–action directly visible in low frequency

 

measurements of the charge stability diagram of tunnel–coupled QDs [3]. Based on this

 

method I will first demonstrate the back–action of driven QPCs on double QDs in the

 

non–equilibrium regime. Then I will present a phonon–spectroscopy measurement that

 

strongly indicates the importance of phonons for non–equilibrium interactions in a mesoscopic environment [4]. Backscattering of an electron defines an upper bound of the

 

energy that can be transferred between an electron and an acoustic phonon (in two dimensions). This limit results in observable features that allow us to determine which part

 

of the back–action of a QPC can be linked to phonon–mediated processes.

 

 

The electron–phonon scattering processes relevant for the phonon–mediated interaction

 

happens in the leads of the driven QPC and stands in direct competition with other scattering mechanisms, e. g. electron–electron scattering. In this context I will present data showing an avalanche amplification effect caused by electron–electron scattering.

 

 

References

 

[1] E. Onac, F. Balestro, L. H. Willems van Beveren, U. Hartmann, Y.V. Nazarov, L.P.

 

Kouwenhoven, Phys. Rev. Lett. 96, 176601 (2006).

 

[2] S. Gustavsson, M. Studer, R. Leturcq, T. Ihn, K. Ensslin, D.C. Driscoll, A.C. Gossard, Phys. Rev. Lett. 99, 206804 (2007).

 

[3] D. Taubert, M. Pioro–Ladriere, D. Schröer, D. Harbusch, A. S. Sachrajda, S. Ludwig, Phys. Rev. Lett. 100, 176805 (2008).

 

[4] G. J. Schinner, H. P. Tranitz, W. Wegscheider, J. P. Kotthaus, S. Ludwig, Phys. Rev. Lett. 102, 186801 (2009).

 

 

September 15, 2009, 11:00, FENS 2019