Current Noise in an Quantum Point Contact

When electrons traverse a quantum point contact (QPC), they experience strong electron-electron interactions, leading to anomalous behavior for the measured dependendence of the conductance on temperature, magnetic field and source-drain voltage. These anomalous effects are collectively known as the 0.7-anomaly in QPCs [1,2]. They can be well described by modeling the QPC as a one-dimensional chain with short-ranged interactions and onsite energies chosen to describe a smooth potential barrier [3,4]. This project will aim towards numerically computing the current noise within the context of this model, in the absence of interactions, using the Keldysh formalism [5]. In case of rapid progress, an optional last step would be to include the effect of interactions using the functional renormalization group (fRG) approach (a numerical fRG is code available) [5].

Mentor: elias.walter@lmu.de

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[2] L. DiCarlo, Y. Zhang, D. T. McClure, D. J. Reilly, C. M. Marcus, L. N. Pfeiffer and K. W. West Shot-Noise Signatures of 0.7 Structure and Spin in a Quantum Point ContactPhys. Rev. Lett. 97, 036810 (2006).
[3] F. Bauer, J. Heyder, E. Schubert, D. Borowsky, D. Taubert, B. Bruognolo, D. Schuh, W. Wegscheider, J. von Delft and S. Ludwig, Microscopic origin of the 0.7-anomaly in quantum point contacts. Nature 501, 73-78 (2013).
[4] D. H. Schimmel, B. Bruognolo and J. von Delft. Spin Fluctuations in the 0.7 Anomaly in Quantum Point Contacts. Phys. Rev. Lett. 119, 196401 (2017).
[5] A. Tsevas, A Keldysh approach to shot noise in quantum point contacts. Bachelor thesis, Ludwig Maximilian University, Munich (2018).