A5052478740- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Magnetic Properties of Alloys
- Nuclear Physics and Applications
- Superconductivity in MgB2 and Alloys
- Multiferroics and related materials
- Inorganic Chemistry and Materials
- Magnetic properties of thin films
- Atomic and Subatomic Physics Research
- Inorganic Fluorides and Related Compounds
- Crystallization and Solubility Studies
- Quantum, superfluid, helium dynamics
- X-ray Diffraction in Crystallography
- Superconducting Materials and Applications
- Geophysical and Geoelectrical Methods
- Electronic and Structural Properties of Oxides
- Spectroscopy and Laser Applications
- Metallurgical and Alloy Processes
- Solid-state spectroscopy and crystallography
- Gas Sensing Nanomaterials and Sensors
- Radiation Detection and Scintillator Technologies
European Spallation Source
2016-2025
University of Birmingham
2011-2025
Osaka University
2005-2012
University of Geneva
2002-2006
X-ray diffraction measurements show that the high-temperature superconductor ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.54}$, with ortho-II oxygen order, has charge-density-wave order in absence of an applied magnetic field. The dominant wave vector charge density is ${\mathbf{q}}_{\mathrm{CDW}}=\mathbf{(}0,0.328(2),0.5\mathbf{)}$, in-plane component parallel to $\mathbf{b}$ axis (chain direction). It a similar incommensurability observed ortho-VIII and ortho-III samples, which have...
To explore the doping dependence of recently discovered charge density wave (CDW) order in YBa2Cu3Oy, we present a bulk-sensitive high-energy x-ray study for several oxygen concentrations, including strongly underdoped YBa2Cu3O6.44. Combined with previous data around so-called 1/8 doping, show that bulk CDW exists at least hole concentrations (p) CuO2 planes 0.078 <~ p 0.132. This implies close vicinity to quantum critical point spin (SDW) order. In contrast pseudogap temperature T*, onset...
Simultaneous resistivity and a.c.-specific heat measurements have been performed under pressure on single crystalline CeCu2Si2 to over 6 GPa in a hydrostatic helium medium. A series of anomalies were observed around the coinciding with maximum superconducting critical temperature, $T_c^{max}$. These can be linked an abrupt change Ce valence, suggest second quantum point at $P_v \simeq 4.5$ GPa, where valence fluctuations provide pairing mechanism, as opposed spin ambient pressure. Such...
Abstract The application of magnetic fields to layered cuprates suppresses their high-temperature superconducting behaviour and reveals competing ground states. In widely studied underdoped YBa 2 Cu 3 O 6+ x (YBCO), the microscopic nature field-induced electronic structural changes at low temperatures remains unclear. Here we report an X-ray study high-field charge density wave (CDW) in YBCO. For hole dopings ∼0.123, find that a field ( B ∼10 T) induces additional CDW correlations along CuO...
Abstract Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but underlying symmetry breaking and origin of CDW remain unclear. We use X-ray diffraction to determine microscopic structure CDWs in an archetypical YBa 2 Cu 3 O 6.54 at its superconducting transition temperature ∼60 K. find that this material break mirror CuO bilayers. The ionic displacements have two components, which are perpendicular parallel planes, out phase with each...
We report on neutron scattering measurements the vortex lattice of noncentrosymmetric superconductor BiPd. observe existence intermediate mixed state, a region where Meissner and phases coexist, which is feature low <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>κ</a:mi></a:math> type-II superconductors. Following this, we obtain an estimate value <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>κ</b:mi></b:math> using extended London model. Finally, find that...
Many cerium-based heavy fermion (HF) compounds have pressure-temperature phase diagrams in which a superconducting region extends far from magnetic quantum critical point. In at least two compounds, CeCu2Si2 and CeCu2Ge2, an enhancement of the transition temperature was found to coincide with abrupt valence change, strong circumstantial evidence for pairing mediated by valence, or charge transfer, fluctuations. This mechanism, instability, is consequence f-c Coulomb repulsion term U_fc...
We use small-angle neutron scattering to study the superconducting vortex lattice in La${}_{2\ensuremath{-}x}$Sr${}_{x}$CuO${}_{4}$ as a function of doping and magnetic field. show that near optimally coordination coherence length $\ensuremath{\xi}$ are controlled by Van Hove singularity crossing Fermi level Brillouin zone boundary. The properties change dramatically spin-density-wave instability is approached upon underdoping. Bragg glass paradigm provides good description this regime...
The vortex lattice (VL) in the high-$\ensuremath{\kappa}$ superconductor YBa${}_{2}$Cu${}_{3}$O${}_{7}$, at 2 K and with magnetic field parallel to crystal c axis, undergoes a sequence of transitions between different structures as function applied field. However, from structural studies alone, it is not possible determine precisely system anisotropy that governs structures. To address this question, here we report new small-angle neutron scattering measurements both VL structure higher...
We describe a new 17 T cryomagnet for neutron, x-ray or optical experiments with rapid in-situ sample change. Sample temperatures are controllable from < 2 K to 300 in vacuum. Alternatively room temperature bore insert can be used the field centre under atmospheric conditions. Some advantages of this system include very low background scattering due small amount material beam path, cooldown, and fast ramping. Access is available ~10-11 degree cone around direction on both sides.
We report further resistive measurements under pressure of samples iron from multiple sources. The normal state resistivity ε-iron varied as ρ0+AT5/3 at low temperature over the entire superconducting domain. superconductivity could be destroyed by mechanical work, and was restored annealing, demonstrating sensitivity to residual ρ0. There is a strong correlation between ρ0 A coefficients critical Tc. field Bc2 corresponding maximum Tc found 0.73 T, implying coherence length about 20 nm,...
We present a volume-sensitive high-energy x-ray diffraction study of the underdoped cuprate high temperature superconductor La2-xSrxCuO4 (x = 0.12, Tc=27 K) in applied magnetic field. Bulk short-range charge stripe order with propagation vector q_ch (0.231, 0, 0.5) is demonstrated to exist below T_ch 85(10) K and shown compete superconductivity. argue that bulk ordering arises from fluctuating stripes become pinned near boundaries between orthorhombic twin domains.
A new method is presented for the analysis of small angle neutron scattering data from quasi-2D systems such as flux lattices, Skyrmion and aligned liquid crystals. significant increase in signal to noise ratio, a natural application Lorentz factor can be achieved by taking advantage knowledge that all relevant centered on plane reciprocal space. The Bayesian form ensures missing information treated controlled way subsequently included analysis. simple algorithm based Gaussian probability...
We present small angle neutron scattering studies of the vortex lattice (VL) in CeCoIn5 with magnetic fields applied parallel (H) to antinodal [100] and nodal [110] directions. For H is [100], a single VL orientation observed, while 90° reorientation transition found for [110]. both field orientations configurations we find distorted hexagonal an anisotropy, Γ=2.0±0.05. The form factor shows strong Pauli paramagnetic effects similar what have previously been reported [001]. At high fields,...
We have observed a magnetic vortex lattice (VL) in BaFe2(As_{0.67}P_{0.33})2 (BFAP) single crystals by small-angle neutron scattering (SANS). With the field along c-axis, nearly isotropic hexagonal VL was formed range from 1 to 16 T, which is record for this technique pnictides, and no symmetry changes were observed. The temperature-dependence of signal measured confirms presence (non d-wave) nodes superconducting gap structure measurements at 5 T below. nodal effects suppressed high fields....
The magnetically frustrated spin ice family of materials is host to numerous exotic phenomena such as magnetic monopole excitations and macroscopic residual entropy extending low temperature. A finite-temperature ordering transition in the absence applied fields has not been experimentally observed classical ${\mathrm{Dy}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ ${\mathrm{Ho}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$. Such a could be induced by application pressure, this work we consider effects...
We report resistivity and calorimetric measurements on two single crystals of CePd2Si2 pressurized up to 7.4 GPa. A weak uniaxial stress induced in the pressure cell demonstrates sensitivity physics anisotropy. Stress applied along c-axis extends whole phase diagram higher pressures enhances superconducting emerging around magnetic instability, with a 40% increase maximum temperature, Tc, doubled range. Calorimetric demonstrate bulk nature superconductivity.
All underdoped high-temperature cuprate superconductors appear to exhibit charge density wave (CDW) order, but both the underlying symmetry breaking and origin of CDW remain unclear. We use X-ray diffraction determine microscopic structure in an archetypical YBa$_2$Cu$_3$O$_{6.54}$ at its superconducting transition temperature Tc ~ 60 K. find that CDWs present this material break mirror CuO2 bilayers. The ionic displacements a have two components: one perpendicular CuO$_2$ planes, another...
We report on small-angle neutron scattering (SANS) measurements of the vortex lattice (VL) in twin-free $\mathrm{YBa}{}_{2}\mathrm{Cu}{}_{3}\mathrm{O}{}_{7}$, extending previously investigated maximum magnetic field 11 T up to 16.7 with applied parallel c axis. This is a microscopic study matter this region superconducting phase. find that high VL displays rhombic structure, field-dependent coordination passes through square configuration no lock-in field-independent structure. The pinning...
Using small angle neutron scattering, the anisotropy of magnetic vortex lattice (VL), in heavily hole-doped pnictide superconductor ${\text{KFe}}_{2}{\text{As}}_{2}$, was studied. Well-ordered VL scattering patterns were measured with fields applied directions between $\mathbf{B}\ensuremath{\parallel}\mathbf{c}$ and basal plane, rotating either towards $[100]$ or $[110]$. Slightly distorted hexagonal observed when $\mathbf{B}\ensuremath{\parallel}\mathbf{c}$. However, pattern more strongly...