| 1. |
- Berholts, Marta, et al.
(författare)
-
Quantum watch and its intrinsic proof of accuracy
- 2022
-
Ingår i: Physical Review Research. - : American Physical Society. - 2643-1564. ; 4:4
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the rich dynamics of complex wave packets composed of multiple high-lying Rydbergstates in He. A quantitative agreement is found between theory and time-resolved photoelectron spectroscopyexperiments. We show that the intricate time dependence of such wave packets can be used for investigatingquantum defects and performing artifact-free timekeeping. The latter relies on the unique fingerprint that iscreated by the time-dependent photoionization of these complex wave packets. These fingerprints determinehow much time has passed since the wave packet was formed and provide an assurance that the measured time iscorrect. Unlike any other clock, this quantum watch does not utilize a counter and is fully quantum mechanicalin its nature. The quantum watch has the potential to become an invaluable tool in pump-probe spectroscopy dueto its simplicity, assurance of accuracy, and ability to provide an absolute timestamp, i.e., there is no need to findtime zero.
|
|
| 2. |
- Giorgianni, Flavio, et al.
(författare)
-
Melting of magnetic order in NaOsO3 by femtosecond laser pulses
- 2022
-
Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 105:15
-
Tidskriftsartikel (refereegranskat)abstract
- NaOsO3 has recently attracted significant attention for the strong coupling between its electronic band structure and magnetic ordering. Here, we used time-resolved magnetic x-ray diffraction to determine the timescale of the photoinduced antiferromagnetic dynamics in NaOsO3. Our measurements are consistent with a sub-100 fs melting of the antiferromagnetic long-range order that occurs significantly faster than the lattice dynamics as monitored by the transient change in intensity of selected Bragg structural reflections, which instead show a decrease of intensity on a timescale of several ps.
|
|
| 3. |
- Gupta, Rahul, et al.
(författare)
-
Element-resolved evidence of superdiffusive spin current arising from ultrafast demagnetization process
- 2023
-
Ingår i: Phys. Rev. B. - : American Physical Society. ; 108:6
-
Tidskriftsartikel (refereegranskat)abstract
- Using element-specific measurements of the ultrafast demagnetization of Ru/Fe65Co35 hetero-structures, we show that Ru can exhibit a significant magnetic contrast (3% asymmetry) resulting from ultrafast spin currents emanating from the demagnetization process of the FeCo layer. We use this magnetic contrast to investigate how superdiffusive spin currents are affected by the doping of heavy elements in the FeCo layer. We find that the spin currents are strongly suppressed, and that the recovery process in Ru slows down by Re doping. This is in accordance with a change in interface reflectivity of spin currents as found by the superdiffusive spin transport model.
|
|
| 4. |
|
|
| 5. |
- Klionsky, Daniel J., et al.
(författare)
-
Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
-
Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
-
Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
|
|
| 6. |
- Liu, H., et al.
(författare)
-
Optical and extreme UV studies of spin dynamics in metallic and insulating ferrimagnets
- 2021
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 130:24
-
Tidskriftsartikel (refereegranskat)abstract
- We present all-optical studies of spin dynamics in two classes of ferrimagnets. Both sets of experiments use table-top laser-based pump–probe techniques to examine the ultrafast and longer timescale spin excitations. We use the visible/near infra-red time-resolved magneto-optical Kerr effect (tr-MOKE) to follow the spin dynamics of a series of metallic (FeCo)1−xGdx thin films with varying Gd content. Magnetic compensation in the films occurs at a Gd concentration of ≈26%, and the spin dynamics of the films exhibit a non-monotonic variation in effective magnetization. We also examine spin dynamics in an insulating NiFe2O4 spinel using ultrafast techniques up at extreme ultraviolet energies, which permit element-specific investigations. The element and time-resolved delay scans reveal a non-trivial interaction between spin excitations on the different magnetic sub-lattices of the magnetic insulator.
|
|
| 7. |
- Pal, Semanti, et al.
(författare)
-
Field-dependent spin waves in high-aspect-ratio single-crystal ferromagnetic nanowires
- 2016
-
Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 9:5, s. 1426-1433
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the spin wave (SW) modes in high-aspect-ratio single-crystal ferromagnetic nanowires (FMNWs) using an all-optical time-resolved magnetooptical Kerr effect (TR-MOKE) microscope. The precessional magnetization dynamics in such FMNWs unveil the presence of uniform and quantized SW modes that can be tuned by varying the bias magnetic field (H). The frequencies of the modes are observed to decrease systematically with a decreasing magnetic field, and the number of modes in the spectrum is reduced from four to three for H < 0.7 kOe. To understand these results, we perform micromagnetic simulations that reveal the presence of edge, standing wave, and uniform SW modes in the nanowires (NWs). Our simulations clearly show how the standing wave and uniform SW modes coalesce to form a single mode with uniform precession over the entire NW for H < 0.7 kOe, reproducing the experimentally observed reduction in modes. Our study elucidates the possibility of manipulating the SW modes in magnetic nanostructures, which is useful for applications in magnonic and spintronic devices.
|
|
| 8. |
- Saha, Susmita, et al.
(författare)
-
Spin-Wave Dynamics and Symmetry Breaking in an Artificial Spin Ice
- 2021
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:6, s. 2382-2389
-
Tidskriftsartikel (refereegranskat)abstract
- Artificial spin ices are periodic arrangements of interacting nanomagnets which allow investigating emergent phenomena in the presence of geometric frustration. Recently, it has been shown that artificial spin ices can be used as building blocks for creating functional materials, such as magnonic crystals. We investigate the magnetization dynamics in a system exhibiting anisotropic magnetostatic interactions owing to locally broken structural inversion symmetry. We find a rich spin-wave spectrum and investigate its evolution in an external magnetic field. We determine the evolution of individual modes, from building blocks up to larger arrays, highlighting the role of symmetry breaking in defining the mode profiles. Moreover, we demonstrate that the mode spectra exhibit signatures of long-range interactions in the system. These results contribute to the understanding of magnetization dynamics in spin ices beyond the kagome and square ice geometries and are relevant for the realization of reconfigurable magnonic crystals based on spin ices.
|
|
