| 1. |
- Berggren, Karl-Fredrik, 1937-, et al.
(författare)
-
Effects of electron interactions at crossings of Zeeman-split subbands in quantum wires
- 2005
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 71:11, s. 115303-1-115303-5
-
Tidskriftsartikel (refereegranskat)abstract
- Recent experimental studies of Zeeman-split one-dimensional subbands in ballistic quantum wires in an in-plane magnetic field show that additional nonquantized conductance structures occur as subbands cross at low electron densities [A. C. Graham et al., Phys. Rev.Lett. 91, 136404 (2003)]. These structures are called 0.7 analogs. We analyze the experimental transconductance data within the Kohn-Sham spin-density-functional method, including exchange and correlation effects for an infinite split-gate quantum wire in a parallel, in-plane magnetic field B∥. Energy levels are found to rearrange abruptly as they cross due to polarization effects driven by exchange and Coulomb interactions. Experimental qualitative features are explained well by this model. ©2005 The American Physical Society.
|
|
| 2. |
|
|
| 3. |
- Jaksch, Peter, 1978-
(författare)
-
Interactions, initial states, and low-dimensional semiconductors
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with different aspects of quantum mechanical interactions. The first part of the thesis focuses on their effects in low-dimensional semiconductors; the second part on one of their applications: quantum algorithms, which utilize superpositions created from quantum mechanical interactions. Bridging the gap between these two slightly different areas is a method for implementing quantum gates using interactions in low-dimensional semiconductors. We address the issue of dimensionality by studying the local density of states in a quantum point contact (QPC). This is important since many results regarding electron transport through the QPC rely on as assumption of one-dimensionality. We show that in order for this assumption to be valid, certain conditions regarding the shape of the potential have to be fulfilled (Paper I). We also study electron transport in quantum wires and QPCs, with emphasis on electron-electron interaction effects, using Density Functional Theory (DFT). In Paper II we provide an explanation of the experimentally observed 0.7 analogues in quantum wires in strong magnetic fields. We show that their origin is intimately linked with the exchange-correlation energy, and is thus as spin polarization phenomenon. In Paper III we analyze the conductance properties of QPCs and claim that spontaneous spin polarization is the driving mechanism behind the 0.7 anomaly in long QPCs. We also investigate the validity of the "Reilly model", and extend the study to nonzero temperature. Furthermore, we investigate the trapping of spin-polarized electrons in edge states around a pair of antidots (Paper IV). This study supports a proposal for using the trapped electrons to realize quantum gates – the building blocks of a quantum computer. The main advantage of our proposal is that the edge states have a very long lifetime, which will reduce problems with decoherence. Papers V and VI, finally, are concerned with quantum algorithms for initial state preparation. In Paper V a method is devised for preparing initial states for quantum eigenvalue calculation; it is based on a scheme for extending the size of a quantum register through duplication of its quantum bits (qubits). The central result in Paper VI is an algorithm for preparing initial states for quantum simulation. The state to be prepared is chosen as an eigenstate, with eigenvalu 0, of some quantum system, on which eigenvalue calculation is performed using the method in Paper V.
|
|
| 4. |
|
|
| 5. |
- Jaksch, Peter, 1978-
(författare)
-
Spin and charge in low-dimensional semiconductors
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we investigate the trapping of spin-polarized electrons in edge states around a pair of antidots (Paper I). This study supports a proposal for using the trapped electrons to realize quantum gates - the building blocks of a quantum computer. The main advantage of our proposal is that the edge states have a very long lifetime, which will reduce problems with decoherence.We also address the issue of dimensionality by studying the local density of states in a quantum point contact (QPC). This is important since many results, regarding electron transport through the QPC, rely on an assumption of one dimensionality. We show that in order for this assumption to be valid, certain conditions regarding the shape of the potential have to be fulfilled (Paper II).Furthermore, we study electron transport in quantum wires, with emphasis on electron-electron interaction effects. In Papers III and IV we provide an explanation, based on these effects, of the experimentally observed 0.7 analogues, using Density Functional Theory (DFT).
|
|
