A5010351889- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Topological Materials and Phenomena
- Magnetic properties of thin films
- Magnetic Properties of Alloys
- Atomic and Subatomic Physics Research
- High-pressure geophysics and materials
- Nuclear Physics and Applications
- Organic and Molecular Conductors Research
- Inorganic Fluorides and Related Compounds
- X-ray Diffraction in Crystallography
- Advanced Chemical Physics Studies
- Magnetism in coordination complexes
- Electronic and Structural Properties of Oxides
- Quantum, superfluid, helium dynamics
- Inorganic Chemistry and Materials
- Geological and Geophysical Studies
- Solid-state spectroscopy and crystallography
- Algebraic structures and combinatorial models
- Advanced NMR Techniques and Applications
- Quantum many-body systems
- Catalysis and Oxidation Reactions
Paul Scherrer Institute
2016-2025
Brookhaven National Laboratory
2018-2022
KTH Royal Institute of Technology
2021
The discovery of superconductivity in a $d^{9-{\delta}}$ nickelate has inspired disparate theoretical perspectives regarding the essential physics this class materials. A key issue is magnitude magnetic superexchange, which relates to whether cuprate-like high-temperature could be realized. We address question using Ni L-edge and O K-edge spectroscopy reduced trilayer $d^{9-1/3}$ La4Ni3O8 associated modeling. magnon energy scale ~80 meV resulting from nearest-neighbor exchange $J = 69(4)4$...
Quantum matter phases may co-exist microscopically even when they display competing tendencies. A fundamental question is whether such a competition can be avoided through the elimination of one phase while other condenses into ground state. Here, we present high-resolution neutron spectroscopy study low-energy spin excitations in high-temperature superconductor La1.855Sr0.145CuO4. In normal state, find magnetic fluctuations at incommensurate reciprocal lattice positions where...
A layered triangular lattice with spin-1/2 ions is an ideal platform to explore highly entangled exotic states like quantum spin liquid (QSL). Here, we report a systematic in-field neutron scattering study on perfect two-dimensional triangular-lattice antiferromagnet, CsYbSe$_2$, member of the large QSL candidate family rare-earth chalcogenides. The elastic measured down 70 mK shows that there short-range 120$^{\circ}$ magnetic order at zero field. In field-induced ordered states, spin-spin...
The discovery of charge-density-wave-related effects in the resonant inelastic x-ray scattering spectra cuprates holds tantalizing promise clarifying interactions that stabilize electronic order. Here, we report a comprehensive study ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ finding charge-density wave persist up to remarkably high doping level $x=0.21$ before disappearing at $x=0.25$. excitation remain essentially unchanged with despite crossing topological...
We report on the commissioning results of cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle Multi-Energy Analysis) at Swiss Spallation Neutron Source Paul Scherrer Institut, Switzerland. is optimized for efficient data acquisition scattered neutrons in horizontal scattering plane, allowing detailed and rapid mapping low-energy excitations under extreme sample environment conditions.
The Kitaev quantum spin liquid epitomizes an entangled topological state, for which two flavors of fractionalized low-energy excitations are predicted: the itinerant Majorana fermion and Z2 gauge flux. It was proposed recently that fingerprints fractional encoded in phonon spectra liquids through a novel fractional-excitation-phonon coupling. Here, we detect anomalous effects α-RuCl3 using inelastic X-ray scattering with meV resolution. At high temperature, discover interlaced optical...
Although ultrafast manipulation of magnetism holds great promise for new physical phenomena and applications, targeting specific states is held back by our limited understanding how magnetic correlations evolve on timescales. Using resonant inelastic x-ray scattering we demonstrate that femtosecond laser pulses can excite transient magnons at large wavevectors in gapped antiferromagnets, they persist several picoseconds which opposite to what observed nearly gapless magnets. Our work...
Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse fluctuations may enhance the inter-stripe Josephson coupling and thus promote Direct experimental studies of dynamics, however, remain difficult. From a strong-coupling perspective, are realized in form dynamic "kinks"-sideways shifting sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment. Our starting point La1.88Sr0.12CuO4 where ordering results...
Abstract In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with commensuration of eight four lattice units, respectively. How this evolves across optimal doping remains controversial question. Here we present systematic resonant inelastic x-ray scattering study weak correlations in La 2− x Sr CuO 4 1.8− Eu 0.2 . Ultra high energy resolution experiments demonstrate the importance separation elastic processes. Long-range...
Abstract The detailed anisotropic dispersion of the low-temperature, low-energy magnetic excitations candidate spin-triplet superconductor UTe 2 is revealed using inelastic neutron scattering. emerge from Brillouin zone boundary at high symmetry Y and T points disperse along crystallographic $$\hat{b}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mo>̂</mml:mo> </mml:mover> </mml:math> -axis. In applied fields to least μ...
Here we present experimental evidence of the pseudo-doublet ground state non-Kramers compound SrTm2O4, based on specific heat, magnetic entropy and electron paramagnetic resonance. We demonstrate that two crystallographic Tm3+ sites give rise to distinct single-ion anisotropies, by extension, SrTm2O4 hosts sublattices. Inelastic neutron scattering reveals low-lying dispersing crystal-field excitations, which modelled using an effective charge model mean field random phase approximation. The...
Although magnetic frustration in metals provides a promising avenue for novel quantum phenomena, their microscopic interpretation is often challenging. Here we use the face-centered cubic intermetallic HoInCu$_4$ as model material to show that Hamiltonians neglecting charge degree of freedom are appropriate frustrated possessing low density states at Fermi surface. Through neutron scattering techniques determine matching exchange interactions paramagnetic and field-polarized using an...
We investigated the crystal structure and lattice excitations of ternary intermetallic stannide ${\mathrm{Ca}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Sn}}_{13}$ using neutron x-ray scattering techniques. For $T>{T}^{*}\ensuremath{\approx}38$ K, diffraction data can be satisfactorily refined space group $Pm\overline{3}n$. Below ${T}^{*}$, is modulated with a propagation vector $\stackrel{P\vec}{q}=(1/2,1/2,0)$. This may arise from merohedral twinning in which three tetragonal domains overlap to mimic...
Excitonic insulators are usually considered to form via the condensation of a soft charge mode bound electron-hole pairs. This, however, presumes that exciton is spin-singlet character. Early theoretical considerations have also predicted very distinct scenario, in which magnetic excitons results an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements Sr3Ir2O7. By isolating longitudinal component spectra, identify well-defined at...
The recent discovery of the topologically protected surface states in beta-phase PdBi2 has reignited research interest this class superconductors. Here, we show results our muon spin relaxation and rotation (muSR) measurements carried out to investigate superconducting magnetic properties topological effect ground state beta-PdBi2. Zero-field muSR data reveal that no sizeable spontaneous magnetization arises with onset superconductivity implying time reversal symmetry is preserved Further, a...
The coupling of spin, charge and lattice degrees freedom results in the emergence novel states matter across many classes strongly correlated electron materials. A model example is unconventional superconductivity, which widely believed to arise from electrons via spin excitations. In cuprate high-temperature superconductors, interplay also reflected a zoo spin-density wave orders that are intertwined with superconductivity. key question whether different types density waves merely coexist...
Abstract The unconventional normal-state properties of the cuprates are often discussed in terms emergent electronic order that onsets below a putative critical doping x c ≈ 0.19. Charge density wave (CDW) correlations represent one such order; however, experimental evidence for generally spans limited range falls short value , leading to questions regarding its essential relevance. Here, we use X-ray diffraction demonstrate CDW La 2− Sr CuO 4 persist up at least = 0.21. show strong changes...
The rare earth nickelates RNiO3 are metallic at high temperatures and insulating magnetically ordered low temperatures. temperature phase has been predicted to be type II multiferroic, i.e. ferroelectric magnetic order coupled occur simultaneously. Confirmation of those ideas inhibited by the absence experimental data on single crystals. Here we report Raman spectroscopic crystals (R = Y, Er, Ho, Dy, Sm, Nd) for between 10 K 1000 K. Entering observe appearance a large number additional...
We report an excellent realization of the highly nonclassical incommensurate spin-density wave (SDW) state in quantum frustrated antiferromagnetic insulator ${\mathrm{Cs}}_{2}{\mathrm{CoBr}}_{4}$. In contrast to well-known Ising spin chain case, here SDW is stabilized by virtue competing planar in-chain anisotropies and interchain exchange. Adjacent phase a broad $m=1/3$ magnetization plateau that can be seen as commensurate locking into up-up-down (UUD) structure. This represents first...
Abstract Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show strain perpendicular the copper-oxide planes directly interaction charge stripe order and La 1.88 Sr 0.12 CuO 4 (LSCO). Compressive c -axis pressure amplifies within superconducting state, while having no impact on normal state. By contrast, dramatically diminishes...
Negative thermal expansion is an unusual phenomenon appearing in only a handful of materials, but pursuit and mastery the holds great promise for applications across disciplines industries. Here we report use x-ray spectroscopy diffraction to investigate 4f-electronic properties Y-doped SmS employ Kondo volume collapse model interpret results. Our measurements reveal unparalleled decrease bulk Sm valence by over 20% at low temperatures mixed-valent golden phase, which show caused strong...
Spinons are well-known as the elementary excitations of one-dimensional antiferromagnetic chains, but means to realize spinons in higher dimensions is subject intense research. Here, we use resonant x-ray scattering study layered trimer iridate Ba4Ir3O10, which shows no magnetic order down 0.2 K. An emergent spinon continuum observed that can be well-described by XXZ spin-1/2 chains with exchange ~55 meV and a small Ising-like anisotropy. With 2% isovalent Sr doping, appears below TN=130 K...