| 1. |
- Finkelstein-Shapiro, Daniel, et al.
(författare)
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Adiabatic elimination and subspace evolution of open quantum systems
- 2020
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Ingår i: Physical Review A. - 2469-9926. ; 101:4
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Tidskriftsartikel (refereegranskat)abstract
- Efficient descriptions of open quantum systems can be obtained by performing an adiabatic elimination of the fast degrees of freedom and formulating effective operators for the slow degrees of freedom in reduced dimensions. Here, we perform the construction of effective operators in frequency space, and using the final value theorem or alternatively the Keldysh theorem, we provide a correction for the trace of the density matrix which takes into account the non-trace-preserving character of the evolution. We illustrate our results with two different systems, one where the eliminated fast subspace is constituted by a continuous set of states and ones with discrete states. Furthermore, we show that the two models converge for very large dissipation and at coherent population trapping points. Our results also provide an intuitive picture of the correction to the trace of the density matrix as a detailed balance equation.
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| 2. |
- Ghosh, Supriya, et al.
(författare)
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Light-induced defect healing and strong many-body interactions in formamidinium lead bromide perovskite nanocrystals
- 2020
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 11:4, s. 1239-1246
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Tidskriftsartikel (refereegranskat)abstract
- Organic lead halide perovskite (OLHP) nanocrystals (NCs) have paved the way to advanced optoelectronic devices through their extraordinary electrical and optical properties. However, understanding of the light-induced complex dynamic phenomena in OLHP NCs remains a subject of debate. Here we used wide field microscopy and time-resolved spectroscopy to correlate the local changes in photophysics and the dynamical behavior of photocarriers. We demonstrate that light-induced brightening of the photoluminescence from the formamidinium lead bromide NC films is related to the film preparation condition and reduction of trap density. The density of trap states is reduced via halide ion migration from interstitial position. Our femtosecond transient absorption study identifies transient Stark effect due to the generation of hot carriers. Because of slow carrier trapping, Auger recombination through many-body carrier-carrier interactions dominates over trion recombination. This work presents unprecedented insights into the light-driven processes enabling better device design in the future.
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| 3. |
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| 4. |
- Liu, Yang, et al.
(författare)
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Defect State Assisted Z-scheme Charge Recombination in Bi2O2CO3/Graphene Quantum Dot Composites for Photocatalytic Oxidation of NO
- 2020
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 3:1, s. 772-781
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we explored the photoinduced charge carriers dynamics rationalizing the photocatalytic oxidation of NO over N-doped Bi2O2CO3/graphene quantum dots composites(N-BOC/GQDs) via time-resolved photoluminescence (TRPL). Under visible light illumination, only GQDs can be photoexcited and inject electrons to N-BOC within 0.5 ns. Under UV light irradiation, the interfacial Z-scheme heterojunction recombination between the electrons in N-BOC and holes in GQDs dominate the depopulation of excited states within 0.36 ns. Such efficient Z-scheme recombination regardless of the large energy difference (1.66 eV) is mediated by the interfacial oxygen vacany defect states characterized by both density functional theory calculations (DFT) and electron paramagnetic resonance (EPR) measurement. This finding provide a novel strategic view to improve the photocatalytic performance of the nanocomposite by interfacial engineering
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| 5. |
- Saideh, Ibrahim, et al.
(författare)
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Projection-based adiabatic elimination of bipartite open quantum systems
- 2020
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Ingår i: Physical Review A. - 2469-9926. ; 102:3
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Tidskriftsartikel (refereegranskat)abstract
- Adiabatic elimination methods allow the reduction of the space dimension needed to describe systems whose dynamics exhibit separation of timescale. For open quantum systems, it consists in eliminating the fast part assuming it has almost instantaneously reached its steady state and obtaining an approximation of the evolution of the slow part. These methods can be applied to eliminate a linear subspace within the system Hilbert space or, alternatively, to eliminate a fast subsystem in a bipartite quantum system. In this work, we extend an adiabatic elimination method used for removing fast degrees of freedom within a system [Phys. Rev. A 101, 042102 (2020)2469-992610.1103/PhysRevA.101.042102] to eliminate a subsystem from an open bipartite quantum system. As an illustration, we apply our technique to a dispersively coupled two-qubit system and in the case of the open Rabi model.
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| 6. |
- Yan, Yajie, et al.
(författare)
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Advancing Tin Halide Perovskites : Strategies toward the ASnX3Paradigm for Efficient and Durable Optoelectronics
- 2020
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Ingår i: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 5:6, s. 2052-2086
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Forskningsöversikt (refereegranskat)abstract
- Various less-toxic substitutes for the Pb2+-based perovskites have been proposed, of which Sn2+-based metal halide perovskites (namely, Sn-PVSKs) hold the best prospects because of their optoelectronic properties comparable to those of the Pb analogues. Nevertheless, the intrinsic instability and unfavorable crystallization of Sn-PVSKs place restrictions on both the device performance/durability and the fabrication reproducibility/large-scale manufacturing, respectively. Therefore, numerous attempts have been directed at exploring the underlying mechanisms of Sn-PVSKs and acquiring high-quality, ambient-stable thin films. In this work, an overview is first given on the milestones and general properties of the paradigm ABX3-structured Sn-PVSKs. Then, their electronic structure evolution, photophysics process, and degradation pathways are thoroughly interpreted. The gained understanding triggers various strategies exploited in the categories of synthetic conditions, compositions, phase components, and device architecture for diverse optoelectronic applications. The final section summarizes key advances in Sn-PVSKs and offers guidance for future improvements that depend critically on these methodologies.
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