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Transport physics

We focus on experimental and theoretical studies of transport and quantum many-body physics, as well as on application aspects of nanostructures and quantum devices made from semiconductor heterostructures and nanowires, and emerging new materials.

Project areas:

Quantum dots in nanowires

We explore the physics of strongly confined quantum dots in semiconductor nanowires, formed by heterostructures and/or local gate potentials. Quantum dots behave as artificial atoms but with properties that can be changed during the experiments using electric and magnetic fields. Our primary focus is on understanding and controlling spin and orbital states in quantum dots and coupled quantum dots, which are key building blocks in many concepts for quantum information processing. We focus on nanowires because they already provide much of the required confinement and offer built-in contacts for transport measurements. Additionally, many interesting materials and heterostructures can only be synthesized in nanowires.

 

SEM photography of two quantum dots in a nanowire

SEM image of an InAs nanowire with GaSb shell grown preferentially on zinc blende InAs (left). SEM image of quantum device showing position of gate electrodes and source-drain contacts to individually control each dot (right). Adapted from D. Barker et al, Appl. Phys. Lett. 114, 183502 (2019); https://doi.org/10.1063/1.5089275

Simulation schemes for quantum transport

We develop numerical tools for a quantitative simulation for electrical transport in nano-devices. Here we use a variety of different approaches ranging from the Pauli master equation, over different types of quantum master equations to Green's function approaches. In this context we established the open source code QMEQ which allows to compare different schemes. Our simulations are targeted to specific experimental designs and allow both to understand the underlying physics and to optimize electro-optical devices.

Key publications

Individually addressable double quantum dots formed with nanowire polytypes and identified by epitaxial markers. D. Barker, S. Lehmann, L. Namazi, M. Nilsson, C. Thelander, K. A. Dick, and V. F. Maisi. Appl. Phys. Lett. 114, 183502 (2019); https://doi.org/10.1063/1.5089275.
See article individually addressable double quantum dots at publisher's site

Kinetic equations for transport through single-molecule transistors. M. Leijnse, M. R. Wegewijs, Physical Review B 78, 235424 (2008).
See article kinetic equations at publisher's site

QmeQ 1.0: An open-source Python package for calculations of transport through quantum dot devices G. Kiršanskas, J. Nyvold Pedersen, O. Karlström, M. Leijnse, A. Wacker, Computer Physics Communications 221, 317 (2017).
See article open-source Python package at publisher's site

Electronic structure of quantum dots. S. M. Reimann and M. Manninen, Rev. Mod. Phys. 74, 1283, (2002)
See article electronic structure of quantum dots at publisher's site

Parallel-Coupled Quantum Dots in InAs Nanowires. M. Nilsson, I.-J. Chen, S. Lehmann, V. Maulerova, K. A. Dick, C. Thelander, Nano Letters 17, 7847 (2017)
See article parallel-coupled quantum dots at publisher's site

Tuning the two-electron hybridization and spin states in parallel-coupled InAs quantum dots. M. Nilsson, F. Viñas Boström, S. Lehmann, K. A. Dick, M. Leijnse, C. Thelander, Phys. Rev. Lett. 121, 156802 (2018).
See article tuning the two-electron hybridization and spin states at publisher's site

Key faculty

Recent theses

Gunnar Eriksson, Solitons, vortices and shell structure in ultracold atomic quantum systems PhD Thesis, Lund University 2020
See Gunnar Eriksson's thesis at the Research Portal

Florinda Viñas Boström, Theory of electronic structure and transport in heterostructure nanowires, PhD Thesis, Lund University 2020
See Florinda Viñas Boström's thesis at the Research Portal

Bahareh Goldozian, Interactions and Coherences in Electron Transport through Serially Coupled Quantum Dots, PhD Thesis, Lund University 2019
See Bahareh Goldozian's thesis at the Research Portal

Fredrik Brange, Quantum Correlations and Temperature Fluctuations in Nanoscale Systems PhD Thesis, Lund University 2019
See Fredrik Brange's thesis at the Research Portal

Malin Nilsson, Charge and Spin Transport in Parallel-Coupled Quantum Dots in Nanowires PhD Thesis, Lund University 2018
See Malin Nilsson's thesis at the Research Portal

Chunlin Yu, Quantum Transport in Superconductor-Semiconductor Nanowire Hybrid Devices PhD Thesis, Lund University 2018
See Chunlin Yu's thesis at the Research Portal