Publications


Nodal multigap superconductivity in KCa2Fe4As4F2

Physical Review B 97 (2018) 060509(R)

M Smidman, FKK Kirschner, DT Adroja, AD Hillier, F Lang, Z-C Zhang, G-H Cao, SJ Blundell


Multi-band magnetotransport in exfoliated thin films of CuxBi2Se3

Journal of Physics: Condensed Matter, 2018 Institute of Physics Publishing (2018)

JA Alexander-Webber, J Huang, J Beilsten-Edmands, P Cermak, C Drasar, RJ Nicholas, AI Coldea


Implications of bond disorder in a S=1 kagome lattice.

Scientific reports 8 (2018) 4745-4745

JL Manson, J Brambleby, PA Goddard, PM Spurgeon, JA Villa, J Liu, S Ghannadzadeh, F Foronda, J Singleton, T Lancaster, SJ Clark, IO Thomas, F Xiao, RC Williams, FL Pratt, SJ Blundell, CV Topping, C Baines, C Campana, B Noll

Strong hydrogen bonds such as F···H···F offer new strategies to fabricate molecular architectures exhibiting novel structures and properties. Along these lines and, to potentially realize hydrogen-bond mediated superexchange interactions in a frustrated material, we synthesized [H2F]2[Ni3F6(Fpy)12][SbF6]2 (Fpy = 3-fluoropyridine). It was found that positionally-disordered H2F+ ions link neutral NiF2(Fpy)4 moieties into a kagome lattice with perfect 3-fold rotational symmetry. Detailed magnetic investigations combined with density-functional theory (DFT) revealed weak antiferromagnetic interactions (J ~ 0.4 K) and a large positive-D of 8.3 K with ms = 0 lying below ms = ±1. The observed weak magnetic coupling is attributed to bond-disorder of the H2F+ ions which leads to disrupted Ni-F···H-F-H···F-Ni exchange pathways. Despite this result, we argue that networks such as this may be a way forward in designing tunable materials with varying degrees of frustration.


Extreme Sensitivity of a Topochemical Reaction to Cation Substitution: SrVO2H versus SrV1- xTi xO1.5H1.5.

Inorganic chemistry 57 (2018) 2890-2898

M Amano Patino, D Zeng, SJ Blundell, JE McGrady, MA Hayward

The anion-ordered oxide-hydride SrVO2H is an antiferromagnetic insulator due to strong correlations between vanadium d electrons. In an attempt to hole-dope SrVO2H into a metallic state, a strategy of first preparing SrV1- xTi xO3 phases and then converting them to the corresponding SrV1- xTi xO2H phases via reaction with CaH2 was followed. This revealed that the solid solution between SrVO3 and SrTiO3 is only stable at high temperature. In addition, reactions between SrV0.95Ti0.05O3 and CaH2 were observed to yield SrV0.95Ti0.05O1.5H1.5 not SrV0.95Ti0.05O2H. This dramatic change in reactivity for a very modest change in initial chemical composition is attributed to an electronic destabilization of SrVO2H on titanium substitution. Density functional theory calculations indicate that the presence of an anion-ordered, tetragonal SrMO2H phase is uniquely associated with a d2 electron count and that titanium substitution leads to an electronic destabilization of SrV1- xTi xO2H phases, which, ultimately, drives further reaction of SrV1- xTi xO2H to SrV1- xTi xO1.5H1.5. The observed sensitivity of the reaction products to the chemical composition of initial phases highlights some of the difficulties associated with electronically doping metastable materials prepared by topochemical reactions.


LaSr3 NiRuO4 H4 : A 4d Transition-Metal Oxide-Hydride Containing Metal Hydride Sheets.

Angewandte Chemie (International ed. in English) (2018)

L Jin, M Lane, D Zeng, FKK Kirschner, F Lang, P Manuel, SJ Blundell, JE McGrady, MA Hayward

The synthesis of the first 4d transition metal oxide-hydride, LaSr3 NiRuO4 H4 , is prepared via topochemical anion exchange. Neutron diffraction data show that the hydride ions occupy the equatorial anion sites in the host lattice and as a result the Ru and Ni cations are located in a plane containing only hydride ligands, a unique structural feature with obvious parallels to the CuO2 sheets present in the superconducting cuprates. DFT calculations confirm the presence of S=1/2  Ni+ and S=0, Ru2+ centers, but neutron diffraction and μSR data show no evidence for long-range magnetic order between the Ni centers down to 1.8 K. The observed weak inter-cation magnetic coupling can be attributed to poor overlap between Ni 3dz2 and H 1s in the super-exchange pathways.


Comparative study of the magnetic properties of La3Ni2B ' O-9 for B ' = Nb, Ta or Sb

JOURNAL OF SOLID STATE CHEMISTRY 258 (2018) 825-834

C-M Chin, PD Battle, SJ Blundell, E Hunter, F Lang, M Hendrickx, RP Sena, J Hadermann


Author Correction: How to probe the spin contribution to momentum relaxation in topological insulators.

Nature communications 9 (2018) 729-

M-S Nam, BH Williams, Y Chen, S Contera, S Yao, M Lu, Y-F Chen, GA Timco, CA Muryn, REP Winpenny, A Ardavan

The original version of this Article contained an error in the spelling of the author Benjamin H. Williams, which was incorrectly given as Benjamin H. Willams. This has now been corrected in both the PDF and HTML versions of the Article.


How to probe the spin contribution to momentum relaxation in topological insulators (vol 8, 2017)

NATURE COMMUNICATIONS 9 (2018) ARTN 729

M-S Nam, BH Willams, Y Chen, S Contera, S Yao, M Lu, Y-F Chen, GA Timco, CA Muryn, REP Winpenny, A Ardavan


Author Correction: How to probe the spin contribution to momentum relaxation in topological insulators.

Nat Commun 9 (2018) 729-

M-S Nam, BH Williams, Y Chen, S Contera, S Yao, M Lu, Y-F Chen, GA Timco, CA Muryn, REP Winpenny, A Ardavan

The original version of this Article contained an error in the spelling of the author Benjamin H. Williams, which was incorrectly given as Benjamin H. Willams. This has now been corrected in both the PDF and HTML versions of the Article.


Two-gap superconductivity with line nodes in CsCa2Fe4As4F2

PHYSICAL REVIEW B 97 (2018) ARTN 060506

FKK Kirschner, DT Adroja, Z-C Wang, F Lang, M Smidman, PJ Baker, G-H Cao, SJ Blundell


Proposal for the detection of magnetic monopoles in spin ice via nanoscale magnetometry

PHYSICAL REVIEW B 97 (2018) ARTN 140402

FKK Kirschner, F Flicker, A Yacoby, NY Yao, SJ Blundell


The key ingredients of the electronic structure of FeSe

Annual Reviews of Condensed Matter Physics, Vol. 9, 125-146, 2018 (2018)

AI Coldea, MD Watson

FeSe is a fascinating superconducting material at the frontier of research in condensed matter physics. Here we provide an overview on the current understanding of the electronic structure of FeSe, focusing in particular on its low energy electronic structure as determined from angular resolved photoemission spectroscopy, quantum oscillations and magnetotransport measurements of single crystal samples. We discuss the unique place of FeSe amongst iron-based superconductors, being a multi-band system exhibiting strong orbitally-dependent electronic correlations and unusually small Fermi surfaces, prone to different electronic instabilities. We pay particular attention to the evolution of the electronic structure which accompanies the tetragonal-orthorhombic structural distortion of the lattice around 90 K, which stabilizes a unique nematic electronic state. Finally, we discuss how the multi-band multi-orbital nematic electronic structure has an impact on the understanding of the superconductivity, and show that the tunability of the nematic state with chemical and physical pressure will help to disentangle the role of different competing interactions relevant for enhancing superconductivity.


Comparative study of the magnetic properties of La<inf>3</inf>Ni<inf>2</inf>B′O<inf>9</inf>for B′ = Nb, Taor Sb

Journal of Solid State Chemistry 258 (2018) 825-834

CM Chin, PD Battle, SJ Blundell, E Hunter, F Lang, M Hendrickx, R Paria Sena, J Hadermann

© 2017 Elsevier Inc. Polycrystalline samples of La 3 Ni 2 NbO 9 and La 3 Ni 2 TaO 9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (µSR); the latter technique was also applied to La 3 Ni 2 SbO 9 . On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random ⅓Ni/⅔B′ mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La 3 Ni 2 B′O 9 (B′ = Nb or Ta) at 5 K although in each case µSR identified the presence of static spins below 30 K. Magnetometry showed that La 3 Ni 2 NbO 9 behaves as a spin glass below 29 K but significant short-range interactions are present in La 3 Ni 2 TaO 9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure.


Coexistence of magnetism and superconductivity in separate layers of the iron-based superconductor Li1-xFex(OH)Fe1-ySe

PHYSICAL REVIEW B 95 (2017) ARTN 134419

CV Topping, FKK Kirschner, SJ Blundell, PJ Baker, DN Woodruff, F Schild, H Sun, SJ Clarke


Room-temperature helimagnetism in FeGe thin films.

Scientific reports 7 (2017) 123-

SL Zhang, I Stasinopoulos, T Lancaster, F Xiao, A Bauer, F Rucker, AA Baker, AI Figueroa, Z Salman, FL Pratt, SJ Blundell, T Prokscha, A Suter, J Waizner, M Garst, D Grundler, G van der Laan, C Pfleiderer, T Hesjedal

Chiral magnets are promising materials for the realisation of high-density and low-power spintronic memory devices. For these future applications, a key requirement is the synthesis of appropriate materials in the form of thin films ordering well above room temperature. Driven by the Dzyaloshinskii-Moriya interaction, the cubic compound FeGe exhibits helimagnetism with a relatively high transition temperature of 278 K in bulk crystals. We demonstrate that this temperature can be enhanced significantly in thin films. Using x-ray scattering and ferromagnetic resonance techniques, we provide unambiguous experimental evidence for long-wavelength helimagnetic order at room temperature and magnetic properties similar to the bulk material. We obtain α intr = 0.0036 ± 0.0003 at 310 K for the intrinsic damping parameter. We probe the dynamics of the system by means of muon-spin rotation, indicating that the ground state is reached via a freezing out of slow dynamics. Our work paves the way towards the fabrication of thin films of chiral magnets that host certain spin whirls, so-called skyrmions, at room temperature and potentially offer integrability into modern electronics.


Quantum Griffiths Phase Inside the Ferromagnetic Phase of Ni_{1-x}V_{x}.

Physical review letters 118 (2017) 267202-267202

R Wang, A Gebretsadik, S Ubaid-Kassis, A Schroeder, T Vojta, PJ Baker, FL Pratt, SJ Blundell, T Lancaster, I Franke, JS Möller, K Page

We study by means of bulk and local probes the d-metal alloy Ni_{1-x}V_{x} close to the quantum critical concentration, x_{c}≈11.6%, where the ferromagnetic transition temperature vanishes. The magnetization-field curve in the ferromagnetic phase takes an anomalous power-law form with a nonuniversal exponent that is strongly x dependent and mirrors the behavior in the paramagnetic phase. Muon spin rotation experiments demonstrate inhomogeneous magnetic order and indicate the presence of dynamic fluctuating magnetic clusters. These results provide strong evidence for a quantum Griffiths phase on the ferromagnetic side of the quantum phase transition.


Strong Coupling of Microwave Photons to Antiferromagnetic Fluctuations in an Organic Magnet.

Physical review letters 119 (2017) 147701-

M Mergenthaler, J Liu, JJ Le Roy, N Ares, AL Thompson, L Bogani, F Luis, SJ Blundell, T Lancaster, A Ardavan, GAD Briggs, PJ Leek, EA Laird

Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (circuit QED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions. These results show that multispin modes in organic crystals are suitable for circuit QED, offering a platform for their coherent manipulation. They also utilize the circuit QED architecture as a way to probe spin correlations at low temperature.


Quantum-critical spin dynamics in a Tomonaga-Luttinger liquid studied with muon-spin relaxation

PHYSICAL REVIEW B 95 (2017) ARTN 020402

JS Moller, T Lancaster, SJ Blundell, FL Pratt, PJ Baker, F Xiao, RC Williams, W Hayes, MM Turnbul, CP Landee


Emergence, causation and storytelling: Condensed matter physics and the limitations of the human mind

Philosophica 92 (2017) 139-164

SJ Blundell

The physics of matter in the condensed state is concerned with problems in which the number of constituent particles is vastly greater than can be easily comprehended. The inherent physical limitations of the human mind are fundamental and restrict the way in which we can interact with and learn about the universe. This presents challenges for developing scientific explanations that are met by emergent narratives, concepts and arguments that have a nontrivial relationship to the underlying microphysics. By examining examples within condensed matter physics, and also from cellular automata, I show how such emergent narratives efficiently describe elements of reality.


Suppression of electronic correlations by chemical pressure from FeSe to FeS

Phys. Rev. B 96, 121103(R) (2017) American Physical Society (2017)

P Reiss, MD Watson, TK Kim, AA Haghighirad, DN Woodruff, M Bruma, SJ Clarke, AI Coldea

Iron-based chalcogenides are complex superconducting systems in which orbitally-dependent electronic correlations play an important role. Here, using high-resolution angle-resolved photoemission spectroscopy, we investigate the effect of these electronic correlations outside the nematic phase in the tetragonal phase of superconducting FeSe1-xSx (x = 0; 0:18; 1). With increasing sulfur substitution, the Fermi velocities increase significantly and the band renormalizations are suppressed towards a factor of 1.5-2 for FeS. Furthermore, the chemical pressure leads to an increase in the size of the quasi-two dimensional Fermi surface, compared with that of FeSe, however, it remains smaller than the predicted one from first principle calculations for FeS. Our results show that the isoelectronic substitution is an effective way to tune electronic correlations in FeSe1-xSx, being weakened for FeS with a lower superconducting transition temperature. This suggests indirectly that electronic correlations could help to promote higher-Tc superconductivity in FeSe.

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