Static and Fluctuating Magnetic Moments in the Ferroelectric Metal LiOsO3

JPS Conference Proceedings 21 (2018)

FKK Kirschner, F Lang, FL Pratt, T Lancaster, Y Shi, Y Guo, AT Boothroyd, SJ Blundell

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.

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


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

Coupling between Spin and Charge Order Driven by Magnetic Field in Triangular Ising System LuFe2O4+delta

CRYSTALS 8 (2018) ARTN 88

L Ding, F Orlandi, DD Khalyavin, AT Boothroyd, D Prabhakaran, G Balakrishnan, P Manuel

Ab initio calculation of spin fluctuation spectra using time-dependent density functional perturbation theory, plane waves, and pseudopotentials

PHYSICAL REVIEW B 97 (2018) ARTN 024420

K Cao, H Lambert, PG Radaelli, F Giustino

We present an implementation of time-dependent density functional perturbation theory for spin fluctuations, based on plane waves and pseudopotentials. We compute the dynamic spin susceptibility self-consistently by solving the time-dependent Sternheimer equation, within the adiabatic local density approximation to the exchange and correlation kernel. We demonstrate our implementation by calculating the spin susceptibility of representative elemental transition metals, namely bcc Fe, fcc Ni, and bcc Cr. The calculated magnon dispersion relations of Fe and Ni are in agreement with previous work. The calculated spin susceptibility of Cr exhibits a soft-paramagnon instability, indicating the tendency of the Cr spins to condense in an incommensurate spin density wave phase, in agreement with experiment.

Investigation of a Spin Transition in a LaCoO3 Single Crystal by the Method of X-Ray Magnetic Circular Dichroism at the Cobalt K- and L (2,3)-Edges

PHYSICS OF THE SOLID STATE 60 (2018) 288-291

VV Sikolenko, IO Troyanchuk, DV Karpinsky, A Rogalev, F Wilhelm, R Rosenberg, D Prabhakaran, EA Efimova, VV Efimov, SI Tiutiunnikov, IA Bobrikov

Breaking Symmetry with Light: Ultra-Fast Ferroelectricity and Magnetism from Three-Phonon Coupling

Physical review B: Condensed matter and materials physics American Physical Society (2018)

PG Radaelli

A theory describing how ferroic properties can emerge transiently in the ultra-fast regime by breaking symmetry with light through three-phonon coupling is presented. Particular emphasis is placed on the special case when two exactly degenerate mid-infra-red or THz phonons are resonantly pumped, since this situation can give rise to an exactly rectified ferroic response with damping envelopes of ~ 1 ps or less. Light-induced ferroelectricity and ferromagnetism are discussed in this context, and a number of candidate materials that could display these phenomena are proposed. The same analysis is also applied to the interpretation of previous femto-magnetism experiments, performed in different frequency ranges (visible and near-infrared), but sharing similar symmetry characteristics.

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.

Ab initio calculation of spin fluctuation spectra using time dependent density functional perturbation theory, planewaves, and pseudopotentials

Physical review B: Condensed matter and materials physics American Physical Society (2018)

F Giustino, K Cao, P Radaelli

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


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

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

Endohedral Metallofullerene as Molecular High Spin Qubit: Diverse Rabi Cycles in Gd2@C79N.

Journal of the American Chemical Society 140 (2018) 1123-1130

Z Hu, B-W Dong, Z Liu, J-J Liu, J Su, C Yu, J Xiong, D-E Shi, Y Wang, B-W Wang, A Ardavan, Z Shi, S-D Jiang, S Gao

An anisotropic high-spin qubit with long coherence time could scale the quantum system up. It has been proposed that Grover's algorithm can be implemented in such systems. Dimetallic aza[80]fullerenes M2@C79N (M = Y or Gd) possess an unpaired electron located between two metal ions, offering an opportunity to manipulate spin(s) protected in the cage for quantum information processing. Herein, we report the crystallographic determination of Gd2@C79N for the first time. This molecular magnet with a collective high-spin ground state (S = 15/2) generated by strong magnetic coupling (JGd-Rad = 350 ± 20 cm-1) has been unambiguously validated by magnetic susceptibility experiments. Gd2@C79N has quantum coherence and diverse Rabi cycles, allowing arbitrary superposition state manipulation between each adjacent level. The phase memory time reaches 5 μs at 5 K by dynamic decoupling. This molecule fulfills the requirements of Grover's searching algorithm proposed by Leuenberger and Loss.

Tracking a hysteretic and disorder-broadened phase transition via the electromagnon response in improper ferroelectrics


CDW Mosley, D Prabhakaran, J Lloyd-Hughes

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.

Spin dynamics and exchange interactions in CuO measured by neutron scattering

PHYSICAL REVIEW B 97 (2018) ARTN 144401

H Jacobsen, SM Gaw, AJ Princep, E Hamilton, S Toth, RA Ewings, M Enderle, EMH Wheeler, D Prabhakaran, AT Boothroyd

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

Nat Commun 9 (0) 56-

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

Topological insulators exhibit a metallic surface state in which the directions of the carriers' momentum and spin are locked together. This characteristic property, which lies at the heart of proposed applications of topological insulators, protects carriers in the surface state from back-scattering unless the scattering centres are time-reversal symmetry breaking (i.e. magnetic). Here, we introduce a method of probing the effect of magnetic scattering by decorating the surface of topological insulators with molecules, whose magnetic degrees of freedom can be engineered independently of their electrostatic structure. We show that this approach allows us to separate the effects of magnetic and non-magnetic scattering in the perturbative limit. We thereby confirm that the low-temperature conductivity of SmB6 is dominated by a surface state and that the momentum of quasiparticles in this state is particularly sensitive to magnetic scatterers, as expected in a topological insulator.

Folded superstructure and degeneracy-enhanced band gap in the weak-coupling charge density wave system 2H-TaSe2

PHYSICAL REVIEW B 97 (2018) ARTN 115118

YW Li, J Jiang, HF Yang, D Prabhakaran, ZK Liu, LX Yang, YL Chen