| 1. |
- Aspegren, Markus, et al.
(författare)
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Perfect Zeeman Anisotropy in Rotationally Symmetric Quantum Dots with Strong Spin-Orbit Interaction
- 2024
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Ingår i: Nano Letters. - 1530-6984. ; 24:26, s. 7927-7933
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Tidskriftsartikel (refereegranskat)abstract
- In nanoscale structures with rotational symmetry, such as quantum rings, the orbital motion of electrons combined with a spin-orbit interaction can produce a very strong and anisotropic Zeeman effect. Since symmetry is sensitive to electric fields, ring-like geometries provide an opportunity to manipulate magnetic properties over an exceptionally wide range. In this work, we show that it is possible to form rotationally symmetric confinement potentials inside a semiconductor quantum dot, resulting in electron orbitals with large orbital angular momentum and strong spin−orbit interactions. We find complete suppression of Zeeman spin splitting for magnetic fields applied in the quantum dot plane, similar to the expected behavior of an ideal quantum ring. Spin splitting reappears as orbital interactions are activated with symmetry-breaking electric fields. For two valence electrons, representing a common basis for spin-qubits, we find that modulating the rotational symmetry may offer new prospects for realizing tunable protection and interaction of spin-orbital states.
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| 2. |
- Debbarma, Rousan, et al.
(författare)
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Defect guided conduction in graphene-derivatives and MoS2 : Two-dimensional nanomaterial models
- 2021
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Ingår i: Applied Materials Today. - : Elsevier BV. - 2352-9407. ; 23
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Forskningsöversikt (refereegranskat)abstract
- The realization of unique scientific phenomena in two-dimensional nanomaterials (2DNMs) has led to their applications in several electronic fields; making it imperative to understand the conduction mechanism of charge carriers in such systems. Though several studies have been conducted on 2DNMs with pristine crystallinity, the inevitable presence of defects in the crystals requires careful consideration of their effect on 2DNMs’ electrical behavior. Here, we outline the effects of chemical, structural, substrate-induced defects and disorder on the conduction mechanism within 2DNMs, particularly graphene derivatives and MoS2. The conduction mechanisms discussed in this work are thermally activated conduction, nearest neighbor hopping, Efros-Shklovskii variable range hopping, and Mott variable range hopping. This review will be beneficial to the various material scientists studying the electronic properties of two-dimensional nanomaterials.
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| 3. |
- Debbarma, Rousan, et al.
(författare)
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Effects of Parity and Symmetry on the Aharonov-Bohm Phase of a Quantum Ring
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992.
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigate the properties of one-dimensional quantum rings that form near the surface of nanowire quantum dots. In agreement with theoretical predictions, we observe the appearance of forbidden gaps in the evolution of states in a magnetic field as the symmetry of a quantum ring is reduced. For a twofold symmetry, our experiments confirm that orbital states are grouped pairwise. Here, a π-phase shift can be introduced in the Aharonov-Bohm relation by controlling the relative orbital parity using an electric field. Studying rings with higher symmetry, we note exceptionally large orbital contributions to the effective g-factor (up to 300), which are many times higher than those previously reported. These findings show that the properties of a phase-coherent system can be significantly altered by the nanostructure symmetry and its interplay with wave function parity.
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| 4. |
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| 5. |
- Debbarma, Rousan, et al.
(författare)
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Josephson Junction π-0 Transition Induced by Orbital Hybridization in a Double Quantum Dot
- 2023
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Ingår i: Physical Review Letters. - 0031-9007. ; 131:25
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we manipulate the phase shift of a Josephson junction using a parallel double quantum dot (QD). By employing a superconducting quantum interference device, we determine how orbital hybridization and detuning affect the current-phase relation in the Coulomb blockade regime. For weak hybridization between the QDs, we find π junction characteristics if at least one QD has an unpaired electron. Notably the critical current is higher when both QDs have an odd electron occupation. By increasing the inter-QD hybridization the critical current is reduced, until eventually a π-0 transition occurs. A similar transition appears when detuning the QD levels at finite hybridization. Based on a zero-bandwidth model, we argue that both cases of phase-shift transitions can be understood considering an increased weight of states with a double occupancy in the ground state and with the Cooper pair transport dominated by local Andreev reflection.
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| 6. |
- Potts, Heidi, et al.
(författare)
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Large-bias spectroscopy of Yu-Shiba-Rusinov states in a double quantum dot
- 2023
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 34:13
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Tidskriftsartikel (refereegranskat)abstract
- We have performed tunnel transport spectroscopy on a quantum dot (QD) molecule proximitized by a superconducting contact. In such a system, the scattering between QD spins and Bogoliubov quasiparticles leads to the formation of Yu-Shiba-Rusinov (YSR) states within the superconducting gap. In this work, we investigate interactions appearing when one- and two-electron spin states in a double-QD energetically align with the superconducting gap edge. We find that the inter-dot spin-triplet state interacts considerably stronger with the superconductor than the corresponding singlet, pointing to stronger screening. By forming a ring molecule with a significant orbital contribution to the effective g-factor, we observe interactions of all four spin-orbital one-electron states with the superconductor under a weak magnetic field.
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