A5081988442- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Nuclear Physics and Applications
- Magnetic Properties of Alloys
- Quantum many-body systems
- Atomic and Subatomic Physics Research
- Multiferroics and related materials
- High-pressure geophysics and materials
- Magnetic properties of thin films
- Theoretical and Computational Physics
- Radiation Detection and Scintillator Technologies
- Topological Materials and Phenomena
- Advanced NMR Techniques and Applications
- Quantum and electron transport phenomena
- Magnetism in coordination complexes
- Nuclear reactor physics and engineering
- Quantum, superfluid, helium dynamics
- Corporate Taxation and Avoidance
- Inorganic Chemistry and Materials
- Algebraic structures and combinatorial models
- Intellectual Capital and Performance Analysis
- Solid-state spectroscopy and crystallography
Rutherford Appleton Laboratory
2016-2025
Science and Technology Facilities Council
2008-2023
Paul Scherrer Institute
2021
University of Geneva
2021
Helmholtz-Zentrum Berlin für Materialien und Energie
2021
Didcot Community Hospital
2018
Devon History Society
2005-2006
Johns Hopkins University
2005
Institute for Science and International Security
2002
There is great interest in finding materials possessing quasiparticles with topological properties. Such may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence magnons an insulating kagome ferromagnet can a band structure. Our neutron scattering measurements further reveal one of the bands flat due to unique geometry lattice. Spin wave calculations show measured structure follows from simple Heisenberg Hamiltonian...
We apply moderate-high-energy inelastic neutron scattering (INS) measurements to investigate ${\mathrm{Yb}}^{3+}$ crystalline electric field (CEF) levels in the triangular spin-liquid candidate ${\mathrm{YbMgGaO}}_{4}$. Three CEF excitations from ground-state Kramers doublet are centered at energies $\ensuremath{\hbar}\ensuremath{\omega}=39$, 61, and 97 meV agreement with effective spin-$1/2$ $g$ factors experimental heat capacity, but reveal sizable broadening. argue that this broadening...
Abstract Supersymmetry is an algebraic property of a quantum Hamiltonian that, by giving every boson fermionic superpartner and vice versa, may underpin physics beyond the Standard Model. Fractional bosonic quasiparticles are familiar in condensed matter, as spin charge excitations t - J model describing electron dynamics one-dimensional materials, but this type symmetry almost unknown. However, triplet ladder applied magnetic field provide supersymmetric analogue chain. Here we perform...
We report neutron-scattering measurements of cooperative spin excitations in antiferromagnetically ordered ${\text{BaFe}}_{2}{\text{As}}_{2}$, the parent phase an iron pnictide superconductor. The data extend up to $\ensuremath{\sim}100\text{ }\text{meV}$ and show that excitation spectrum is sharp highly dispersive. By fitting a linear spin-wave model we estimate magnon bandwidth be region 0.17 eV. large characteristic spin-fluctuation energy suggests magnetism could play role formation...
We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41 as a starting point for investigating doped ladders and their tendency toward superconductivity. A key feature was separation of one-triplon two-triplon scattering. Two-triplon is observed quantitatively first time so access realized to important strong magnetic quantum fluctuations. The spin gap found be 26.4+/-0.3 meV. data are successfully modeled using continuous unitary transformation...
The spin waves in a powdered sample of quasi-two-dimensional antiferromagnet, FePS(3), have been measured using neutron inelastic scattering. data could be modelled and the exchange interactions determined two-dimensional Heisenberg Hamiltonian with single ion anisotropy. A suitable fit to only achieved by including magnetic up third nearest neighbour, which is consistent findings for other members MPS(3) family (M=transition metal). best parameters at 6 K were J(1) = 1.49 meV, J(2) 0.04...
Since its proposal by Anderson, resonating valence bonds (RVB) formed a superposition of fluctuating singlet pairs have been paradigmatic concept in understanding quantum spin liquids. Here, we show that excitations related to breaking on nearest-neighbour describe the high-energy part excitation spectrum YbMgGaO4, effective spin-1/2 frustrated antiferromagnet triangular lattice, as originally considered Anderson. By thorough single-crystal inelastic neutron scattering study, demonstrate RVB...
The motion of a spin excitation across topologically nontrivial magnetic order exhibits deflection that is analogous to the effect Lorentz force on an electrically charged particle in orbital field. We used polarized inelastic neutron scattering investigate propagation magnons (i.e., bosonic collective excitations) lattice skyrmion tubes manganese silicide. For wave vectors perpendicular tubes, magnon spectra are consistent with formation finely spaced emergent Landau levels characteristic...
Quantum spin liquids (QSLs) have become a key area of research in magnetism due to their remarkable properties, such as long-range entanglement, fractional excitations, and topologically protected phenomena. Recently, the search for QSLs has expanded into three-dimensional world, despite suppression quantum fluctuations high dimensionality. A new candidate material, K2Ni2(SO4)3, belongs langbeinite family consists two interconnected trillium lattices. Although magnetically ordered, it...
We have measured the bulk properties as well elastic and inelastic neutron scattering of ${\mathrm{YMnO}}_{3}$ in order to understand static dynamic Mn moments. Our measurements clearly show that above ${T}_{N}$ there are short range correlations between spins at nearest neighbor next sites, which also fluctuate time. This, together with other properties, demonstrates presence a spin liquid phase arising from geometrically frustrated Below ${T}_{N},$ well-defined wave develops we can...
We report inelastic neutron scattering measurements of the resonant spin excitations in Ba(1-x)K(x)Fe(2)As(2) over a broad range electron band filling. The fall superconducting transition temperature with hole doping coincides magnetic splitting into two incommensurate peaks because growing mismatch and Fermi surface volumes, as confirmed by tight-binding model s(±)-symmetry pairing. reduction nesting is accompanied collapse resonance binding energy its spectral weight, caused weakening...
Inelastic neutron scattering is used to measure the spin excitation spectrum of Heisenberg $S=1/2$ ladder material $({\mathrm{C}}_{7}{\mathrm{H}}_{10}\mathrm{N}{)}_{2}{\mathrm{CuBr}}_{4}$ in its entirety, both gapped liquid and magnetic field-induced Tomonaga-Luttinger regimes. A fundamental change dynamics observed between these two Density matrix renormalization group calculations quantitatively reproduce help understand commensurate incommensurate excitations. The results validate...
We present high-resolution single-crystal time-of-flight neutron scattering measurements on the candidate quantum spin liquid pyrochlore Tb${}_{2}$Ti${}_{2}$O${}_{7}$ at low temperature and in a magnetic field. At $\ensuremath{\sim}70$ mK zero field, reveals diffuse elastic ($\frac{1}{2}$,$\frac{1}{2}$,$\frac{1}{2}$) positions reciprocal space, consistent with short-range correlated regions based two-in, two-out ice configuration doubled conventional unit cell. This is separated from very...
Abstract The quantum spin liquid is a highly entangled magnetic state characterized by the absence of static magnetism in its ground state. Instead, spins fluctuate correlated way down to lowest temperatures. Quantum liquids are very rare and confined few specific cases where interactions between ions cannot be simultaneously satisfied (known as frustration). Lattices with triangular or tetrahedral arrangements, which interact via isotropic antiferromagnetic interactions, can generate such...
The MAPS direct geometry time-of-flight chopper spectrometer at the ISIS pulsed neutron and muon source has been in operation since 1999, its novel use of a large array position-sensitive detectors paved way for later generations spectrometers around world. Almost two decades experience user operations on MAPS, together with lessons learned from new generation instruments, led to decision perform three parallel upgrades instrument. These were replace primary beamline collimation supermirror...
The authors report inelastic neutron scattering measurements to directly visualize the effects of collective quantum fluctuations in a spin-\textonehalf{} near-Heisenberg antiferromagnet on triangular lattice. They observe rich spectrum sharp magnons at low energies with strongly renormalized dispersions and much reduced spectral weight, which are accompanied higher by very strong highly structured continuum excitations. dispersion renormalizations transfer weight states attributed effect...
Neutron diffraction and inelastic spectroscopy is used to characterize the magnetic Hamiltonian of SrHo2O4 SrDy2O4. Through a detailed computation crystal-field levels we find site- dependent anisotropic single-ion magnetism in both materials measurements show presence strong one-dimensional spin correlations. Our indicate that competing interactions zig-zag chain, combined with frustrated interchain interactions, play crucial role stabilizing spin-liquid type correlations this series.