| 1. |
- Dorsch, Sven, et al.
(författare)
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Characterization of electrostatically defined bottom-heated InAs nanowire quantum dot systems
- 2021
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:12
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of temperature gradients to charge currents in quantum dot systems enables probing various concepts from highly efficient energy harvesting and fundamental thermodynamics to spectroscopic possibilities complementary to conventional bias device characterization. In this work, we present a proof-of-concept study of a device architecture where bottom-gates are capacitively coupled to an InAs nanowire and double function as local joule heaters. The device design combines the ability to heat locally at different locations on the device with the electrostatic definition of various quantum dot and barrier configurations. We demonstrate the versatility of this combined gating- and heating approach by studying, as a function of the heater location and bias, the Seebeck effect across the barrier-free nanowire, fit thermocurrents through quantum dots for thermometry and detect the phonon energy using a serial double quantum dot. The results indicate symmetric heating effects when the device is heated with different gates and we present detection schemes for the electronic and phononic heat transfer contribution across the nanowire. Based on this proof-of-principle work, we propose a variety of future experiments.
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| 2. |
- Dorsch, Sven, et al.
(författare)
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Gate control, g factors, and spin-orbit energy of p -type GaSb nanowire quantum dot devices
- 2021
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Ingår i: Physical Review B. - 2469-9950. ; 103:24
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Tidskriftsartikel (refereegranskat)abstract
- Proposals for quantum information applications are frequently based on the coherent manipulation of spins confined to quantum dots. For these applications, p-type III-V material systems promise a reduction of the hyperfine interaction while maintaining large g factors and strong spin-orbit interaction. In this Letter, we study bottom-gated device architectures to realize single and serial multiquantum dot systems in Schottky-contacted p-type GaSb nanowires. We find that the effect of potentials applied to gate electrodes on the nanowire is highly localized to the immediate vicinity of the gate electrode only, which prevents the formation of double quantum dots with commonly used device architectures. We further study the transport properties of a single quantum dot induced by bottom gating and find large gate-voltage dependent variations of the g∗ factors up to 8.1±0.2 as well as spin-orbit energies between 110 and 230 μeV.
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| 3. |
- Dorsch, Sven, et al.
(författare)
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Heat Driven Transport in Serial Double Quantum Dot Devices
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:2, s. 988-994
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Tidskriftsartikel (refereegranskat)abstract
- Studies of thermally induced transport in nanostructures provide access to an exciting regime where fluctuations are relevant, enabling the investigation of fundamental thermodynamic concepts and the realization of thermal energy harvesters. We study a serial double quantum dot formed in an InAs/InP nanowire coupled to two electron reservoirs. By means of a specially designed local metallic joule-heater, the temperature of the phonon bath in the vicinity of the double quantum dot can be enhanced. This results in phonon-assisted transport, enabling the conversion of local heat into electrical power in a nanosized heat engine. Simultaneously, the electron temperatures of the reservoirs are affected, resulting in conventional thermoelectric transport. By detailed modeling and experimentally tuning the interdot coupling, we disentangle both effects. Furthermore, we show that phonon-assisted transport is sensitive to excited states. Our findings demonstrate the versatility of our design to study fluctuations and fundamental nanothermodynamics.
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| 4. |
- Dorsch, Sven
(författare)
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Transport in nanowire-based quantum dot systems: Heating electrons and confining holes
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum dots embedded in an electronic circuit allow precise control over the charge transport behaviour of the system: Charge carriers can be individually trapped or precisely shuffled between a series of quantum dots in a strictly sequential manner. This introduces ideal conditions to study fundamental quantum physics and such devices are in the focus of extensive efforts to develop quantum information related applications. This thesis contributes to the development of model systems enabling control of, and abiding by quantum mechanical effects. The aim of the model systems is to search and use advantages compared to devices governed purely by the laws of classical physics.In this thesis, transport phenomena in n- and p-type III-V semiconductor nanowire quantum dot systems are explored. First, the concepts necessary to build an understanding of charge transport across quantum dot systems, namely quantum confinement in nanostructures and Coulomb blockade, are introduced. Next, the principles of transport across single and double quantum dot devices are discussed and various experimental device designs are presented. The experimental work falls into two separate research directions and the thesis includes three published papers, which are put into context and supplemented with additional experimental results.Paper I characterizes the properties of p-type GaSb nanowires to assess the material's applicability for the realization of spin-orbit qubits as fundamental building blocks of solid state quantum computers. Experimentally, g-factors and the spin-orbit energy are determined and fabricational challenges for the realization of serial double quantum dot devices are discussed and overcome.Papers II and III study thermally driven currents in InAs nanowire double quantum dots, where heat is essentially converted to electrical power. Such nanoscale energy harvesters operate in a regime where fluctuations are highly relevant and give insights into fundamental nanothermodynamic concepts. Thermally induced currents in double quantum dot devices are the result of three-terminal phonon-assisted transport or the two-terminal thermoelectric effect. Paper II studies the interplay of the two effects, the relevance of the interdot coupling and the impact of excited states. Paper III develops a versatile device architecture which combines bottom-gating and heating and enables the localized application of heat along the nanowire axis. Such devices provide ideal, controlled conditions for future studies of fundamental nanothermodynamics.
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