| 1. |
- 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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| 2. |
- 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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| 3. |
- 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
-
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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| 4. |
- Horio, M., et al.
(author)
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Orbital-selective metal skin induced by alkali-metal-dosing Mott-insulating Ca 2 RuO 4
- 2023
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In: Communications Physics. - 2399-3650. ; 6:1
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Journal article (peer-reviewed)abstract
- Doped Mott insulators are the starting point for interesting physics such as high temperature superconductivity and quantum spin liquids. For multi-band Mott insulators, orbital selective ground states have been envisioned. However, orbital selective metals and Mott insulators have been difficult to realize experimentally. Here we demonstrate by photoemission spectroscopy how Ca2RuO4, upon alkali-metal surface doping, develops a single-band metal skin. Our dynamical mean field theory calculations reveal that homogeneous electron doping of Ca2RuO4 results in a multi-band metal. All together, our results provide evidence for an orbital-selective Mott insulator breakdown, which is unachievable via simple electron doping. Supported by a cluster model and cluster perturbation theory calculations, we demonstrate a type of skin metal-insulator transition induced by surface dopants that orbital-selectively hybridize with the bulk Mott state and in turn produce coherent in-gap states.
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| 5. |
- Kobayashi, Takahiro, et al.
(author)
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Revealing the Hidden Spin-Polarized Bands in a Superconducting Tl Bilayer Crystal
- 2023
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In: Nano Letters. - 1530-6992 .- 1530-6984. ; 23:16, s. 7675-7682
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Journal article (peer-reviewed)abstract
- The interplay of spin-orbit coupling and crystal symmetry can generate spin-polarized bands in materials only a few atomic layers thick, potentially leading to unprecedented physical properties. In the case of bilayer materials with global inversion symmetry, locally broken inversion symmetry can generate degenerate spin-polarized bands, in which the spins in each layer are oppositely polarized. Here, we demonstrate that the hidden spins in a Tl bilayer crystal are revealed by growing it on Ag(111) of sizable lattice mismatch, together with the appearance of a remarkable phenomenon unique to centrosymmetric hidden-spin bilayer crystals: a novel band splitting in both spin and space. The key to success in observing this novel splitting is that the interaction at the interface has just the right strength: it does not destroy the original wave functions of the Tl bilayer but is strong enough to induce an energy separation.
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| 6. |
- Kramer, K. P., et al.
(author)
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Revealing the Orbital Composition of Heavy Fermion Quasiparticles in CeRu 2 Si 2
- 2023
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In: Journal of the Physical Society of Japan. - 1347-4073 .- 0031-9015. ; 92:10
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Journal article (peer-reviewed)abstract
- We present a resonant angle-resolved photoemission spectroscopy (ARPES) study of the electronic band structure and heavy fermion quasiparticles in CeRu2Si2. Using light polarization analysis, considerations of the crystal field environment and hybridization between conduction and f electronic states, we identify the d-electronic orbital character of conduction bands crossing the Fermi level. Resonant ARPES spectra suggest that the localized Ce f states hybridize with eg and t2g states around the zone center. In this fashion, we reveal the orbital structure of the heavy fermion quasiparticles in CeRu2Si2 and discuss its implications for metamagnetism and superconductivity in the related compound CeCu2Si2
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| 7. |
- Miniotaite, Ugne, et al.
(author)
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Magnetic Properties of Multifunctional 7 LiFePO 4 under Hydrostatic Pressure
- 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
- LiFePO4 (LFPO) is an archetypical and well-known cathode material for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties. Our team has previously utilized the muon spin rotation (μ +SR) technique to investigate both magnetic spin order as well as Li-ion diffusion in LFPO. In this initial study we extend our investigation and make use of high-pressure μ +SR to investigate effects on the low-T magnetic order. Contrary to theoretical predictions we find that the magnetic ordering temperature as well as the ordered magnetic moment increase at high pressure (compressive strain).
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| 8. |
- Nocerino, E., et al.
(author)
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Competition between magnetic interactions and structural instabilities leading to itinerant frustration in the triangular lattice antiferromagnet LiCrSe 2
- 2023
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In: Communications Materials. - 2662-4443. ; 4:1
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Journal article (peer-reviewed)abstract
- LiCrSe2 constitutes a recent valuable addition to the ensemble of two-dimensional triangular lattice antiferromagnets. In this work, we present a comprehensive study of the low temperature nuclear and magnetic structure established in this material. Being subject to a strong magnetoelastic coupling, LiCrSe2 was found to undergo a first order structural transition from a trigonal crystal system (P3 ¯ m1) to a monoclinic one (C2/m) at T s = 30 K. Such restructuring of the lattice is accompanied by a magnetic transition at T N = 30 K. Refinement of the magnetic structure with neutron diffraction data and complementary muon spin rotation analysis reveal the presence of a complex incommensurate magnetic structure with a up-up-down-down arrangement of the chromium moments with ferromagnetic double chains coupled antiferromagnetically. The spin axial vector is also modulated both in direction and modulus, resulting in a spin density wave-like order with periodic suppression of the chromium moment along the chains. This behavior is believed to appear as a result of strong competition between direct exchange antiferromagnetic and superexchange ferromagnetic couplings established between both nearest neighbor and next nearest neighbor Cr3+ ions. We finally conjecture that the resulting magnetic order is stabilized via subtle vacancy/charge order within the lithium layers, potentially causing a mix of two co-existing magnetic phases within the sample.
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| 9. |
- Nocerino, E., et al.
(author)
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Magnetic nature of wolframite MgReO 4
- 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
- Rhenium oxides belonging to the family AReO4 where A is a metal cation, exhibit interesting electronic and magnetic properties. In this study we have utilized the muon spin rotation/relaxation (μ +SR) technique to study the magnetic properties of the MgReO4 compound. To the best of our knowledge, this is the first investigation reported on this interesting material, that is stabilized in a wolframite crystal structure using a special high-pressure synthesis technique. Bulk magnetic studies show the onset of an antiferromagnetic (AF) long range order, or a possible singlet spin state at T C1 ≈ 90 K, with a subtle second high-temperature transition at T C2 ≈ 280 K. Both transitions are also confirmed by heat capacity (Cp ) measurements. From our μ +SR measurements, it is clear that the sample enters an AF order below T C1 = T N ≈ 85 K. We find no evidence of magnetic signal above T N, which indicates that T C2 is likely linked to a structural transition. Further, via sensitive zero field (ZF) μ +SR measurements we find evidence of a spin reorientation at T Cant ≈ 65 K. This points towards a transition from a collinear AF into a canted AF order at low temperature, which is proposed to be driven by competing magnetic interactions.
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| 10. |
- Nocerino, Elisabetta, et al.
(author)
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Multiple unconventional charge density wave transitions in LaPt2Si2 superconductor clarified with high-energy X-ray diffraction
- 2023
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In: Communications Materials. - : Springer Nature. - 2662-4443. ; 4:1
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Journal article (peer-reviewed)abstract
- The quasi-2D platinum-based rare earth intermetallic LaPt2Si2 has attracted attention as it exhibits strong interplay between charge density wave order and superconductivity. However, most of the results reported on this material come from theoretical calculations, preliminary bulk investigations and powder samples, which makes it difficult to uniquely determine the temperature evolution of its crystal structure and, consequently, of its charge density wave transition. Therefore, the published literature around LaPt2Si2 is often controversial. Here, by means of high-resolution synchrotron X-ray diffraction data, we clarify some of the poorly or partially understood aspects of the physics of LaPt2Si2. In particular, we resolve the complex evolution of its crystal structure and superstructures, identifying the temperature dependence of multiple density wave transitions in good quality LaPt2Si2 single crystals. According to our findings, on cooling from room temperature LaPt2Si2 undergoes a series of subtle structural transitions which can be summarised as follows: second order commensurate tetragonal (P4/n m m)-to-incommensurate structure followed by a first order incommensurate-to-commensurate orthorhombic (P m m n) transition and then a first order commensurate orthorhombic (P m m n)-to-commensurate tetragonal (P4/n m m). The structural transitions are accompanied by both incommensurate and commensurate superstructural distortions of the lattice. The observed behavior is compatible with discommensuration of the CDW in this material.
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