| 1. |
- Jonsson, Viktor, et al.
(author)
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Photoelectron dispersion in metallic and insulating thin films
- 2021
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In: Physical Review Research. - : American Physical Society. - 2643-1564. ; 3:3
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Journal article (peer-reviewed)abstract
- The underlying mechanism behind the metal-to-insulator transition in is still a topic of intense debate. The two leading theoretical interpretations associate the transition with either electron-lattice or electron-electron correlations. Novel experimental results are required to converge towards one of the two scenarios. Here we report on a temperature-dependent angle-resolved photoelectron study of thin films across the metal-to-insulator transition. The obtained experimental results are compared to density functional theory calculations. We find an overall energy shift and compression of the electronic band structure across the transition while the overall band topology is conserved. The results demonstrate the importance of electron-electron correlations in establishing the insulating state.
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| 2. |
- Benedek, Peter, et al.
(author)
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Quantifying Diffusion through Interfaces of Lithium-Ion Battery Active Materials
- 2020
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In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 12:14, s. 16243-16249
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Journal article (peer-reviewed)abstract
- Detailed understanding of charge diffusion processes in a lithium-ion battery is crucial to enable its systematic improvement. Experimental investigation of diffusion at the interface between active particles and the electrolyte is challenging but warrants investigation as it can introduce resistances that, for example, limit the charge and discharge rates. Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy. By performing measurements on LiFePO4 platelets with different sizes, we determine how diffusion through the LiFePO4 (010) interface differs from that in the center of the particle (i.e., bulk diffusion). We perform ab initio calculations to aid the understanding of the results and show the relevance of our interfacial diffusion measurement to electrochemical performance through cyclic voltammetry measurements. These results indicate that surface engineering can be used to improve the performance of lithium-ion batteries.
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| 3. |
- Chen, Chih-Yao, et al.
(author)
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High-voltage honeycomb layered oxide positive electrodes for rechargeable sodium batteries
- 2020
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 56:65, s. 9272-9275
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Journal article (peer-reviewed)abstract
- Honeycomb layered oxides from Na2Ni2-xCoxTeO6 family were assessed for use as positive electrodes in rechargeable sodium batteries at ambient and elevated temperatures using ionic liquids. Substitution of nickel with cobalt increases the discharge voltage to nearly 4 V (versus Na+/Na), surpassing the average voltages of most Na based layered oxide positive electrodes.
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| 4. |
- Duan, Yu Xia, et al.
(author)
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Crystal electric field splitting and f -electron hybridization in heavy-fermion CePt2In7
- 2019
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In: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9969 .- 2469-9950. ; 100:8
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Journal article (peer-reviewed)abstract
- We use high-resolution angle-resolved photoemission spectroscopy to investigate the electronic structure of the antiferromagnetic heavy fermion compound CePt2In7, which is a member of the CeIn3-derived heavy fermion material family. Weak hybridization among 4f electron states and conduction bands was identified in CePt2In7 at low temperature much weaker than that in the other heavy fermion compounds like CeIrIn5 and CeRhIn5. The Ce 4f spectrum shows fine structures near the Fermi energy, reflecting the crystal electric field splitting of the 4f5/21 and 4f7/21 states. Also, we find that the Fermi surface has a strongly three-dimensional topology, in agreement with density-functional theory calculations. © 2019 American Physical Society.
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| 5. |
- Elson, Frank, et al.
(author)
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TRIM Simulations Tool for μ + Stopping Fraction in Hydrostatic Pressure Cells
- 2023
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Conference paper (peer-reviewed)abstract
- For quantum systems or materials, a common procedure for probing their behaviour is to tune electronic/magnetic properties using external parameters, e.g. temperature, magnetic field or pressure. Pressure application as an external stimuli is a widely used tool, where the sample in question is inserted into a pressure cell providing a hydrostatic pressure condition. Such device causes some practical problems when using in Muon Spin Rotation/Relaxation (μ +SR) experiments as a large proportion of the muons will be implanted in the pressure cell rather than in the sample, resulting in a higher background signal. This issue gets further amplified when the temperature dependent response from the sample is much smaller than that of the pressure cell,which may cause the sample response to be lost in the background and cause difficulties in aligning the sample within the beam. To tackle this issue, we have used pySRIM [1] to construct a practical and helpful simulation tool for calculating muon stopping fractions, specifically for the pressure cell setup at the μE1 beamline using the GPD spectrometer at the Paul Scherrer Institute, with the use of TRIM simulations. The program is used to estimate the number of muon stopping in both the sample and the pressure cell at a given momentum. The simultion tool is programmed into a GUI, making it accessible to user to approximate prior to their experiments at GPD what fractions will belong to the sample and the pressure cell in their fitting procedure.
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| 6. |
- Facio, Jorge I., et al.
(author)
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Engineering a pure Dirac regime in ZrTe5
- 2023
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In: SciPost Physics. - : Stichting SciPost. - 2542-4653. ; 14:4
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Journal article (peer-reviewed)abstract
- Real-world topological semimetals typically exhibit Dirac and Weyl nodes that coexist with trivial Fermi pockets. This tends to mask the physics of the relativistic quasiparti-cles. Using the example of ZrTe5, we show that strain provides a powerful tool for in-situ tuning of the band structure such that all trivial pockets are pushed far away from the Fermi energy, but only for a certain range of Van der Waals gaps. Our results naturally reconcile contradicting reports on the presence or absence of additional pockets in ZrTe5, and provide a clear map of where to find a pure three-dimensional Dirac semimetallic phase in the structural parameter space of the material.
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| 7. |
- Forslund, Ola Kenji, et al.
(author)
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Intertwined magnetic sublattices in the double perovskite compound LaSrNiReO6
- 2020
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In: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 102:14
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Journal article (peer-reviewed)abstract
- We report a muon spin rotation (μ+SR) study of the magnetic properties of the double perovskite compound LaSrNiReO6. Using the unique length and time scales of the μ+SR technique, we successfully clarify the magnetic ground state of LaSrNiReO6, which was previously deemed as a spin glass state. Instead, our μ+SR results point toward a long-range dynamically ordered ground state below TC=23 K, for which a static limit is foreseen at T=0. Furthermore, between 23K250 K) state. Our results reveal how two separate yet intertwined magnetic lattices interact within the unique double perovskite structure and the importance of using complementary experimental techniques to obtain a complete understanding of the microscopic magnetic properties of complex materials.
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| 8. |
- Forslund, Ola Kenji, 1990, et al.
(author)
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Pressure driven magnetic order in Sr 1 - x Ca x Co 2 P 2
- 2022
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 12:1
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Journal article (peer-reviewed)abstract
- The magnetic phase diagram of Sr1-xCaxCo2P2 as a function of hydrostatic pressure and temperature is investigated by means of high pressure muon spin rotation, relaxation and resonance (μ+SR). The weak pressure dependence for the x≠ 1 compounds suggests that the rich phase diagram of Sr1-xCaxCo2P2 as a function of x at ambient pressure may not solely be attributed to chemical pressure effects. The x= 1 compound on the other hand reveals a high pressure dependence, where the long range magnetic order is fully suppressed at pc 2≈ 9.8 kbar, which seem to be a first order transition. In addition, an intermediate phase consisting of magnetic domains is formed above pc 1≈ 8 kbar where they co-exist with a magnetically disordered state. These domains are likely to be ferromagnetic islands (FMI) and consist of an high- (FMI-1) and low-temperature (FMI-2) region, respectively, separated by a phase boundary at Ti≈ 20 K. This kind of co-existence is unusual and is originating from a coupling between lattice and magnetic degrees of freedoms.
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| 9. |
- Galeski, S., et al.
(author)
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Origin of the quasi-quantized Hall effect in ZrTe 5
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac semimetal ZrTe . It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe electronic structure and its Dirac-type semi-metallic character.
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| 10. |
- Ge, Yuqing, 1996, et al.
(author)
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Confirming the high pressure phase diagram of the Shastry-Sutherland model
- 2023
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Conference paper (peer-reviewed)abstract
- A Muon Spin Rotation (μ + SR) study was conducted to investigate the magnetic properties of SrCu2(BO3)2 (SCBO) as a function of temperature/pressure. Measurements in zero field and transverse field confirm the absence of long range magnetic order at high pressures and low temperatures. These measurements suggest changes in the Cu spin fluctuations characteristics above 21 kbar, consistent with the formation of a plaquette phase as previously suggested by inelastic neutron scattering measurements. SCBO is the only known realisation of the Shatry-Sutherland model, thus the ground state mediating the dimer and antiferromagnetic phase is likekly to be a plaquette state.
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