Publications


Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe

PHYSICAL REVIEW B 95 , 081106(R) (2017) (2017)

MD Watson, S Backes, AA Haghighirad, M Hoesch, TK Kim, AI Coldea, R Valenti


Codoping of Sb2Te3 thin films with V and Cr

PHYSICAL REVIEW MATERIALS 1 (2017) ARTN 064409

LB Duffy, AI Figueroa, G van der Laan, T Hesjedal


Correction to Step-Flow Growth of Bi 2 Te 3 Nanobelts

Crystal Growth & Design 17 (2017) 1438-1438

P Schönherr, T Tilbury, H Wang, AA Haghighirad, V Srot, PA van Aken, T Hesjedal


Temperature-induced phase transition from cycloidal to collinear antiferromagnetism in multiferroic Bi0.9Sm0.1FeO3 driven by f-d induced magnetic anisotropy

PHYSICAL REVIEW B 95 (2017) ARTN 054420

RD Johnson, PA McClarty, DD Khalyavin, P Manuel, P Svedlindh, CS Knee


Proposal of a micromagnetic standard problem for ferromagnetic resonance simulations

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 421 (2017) 428-439

A Baker, M Beg, G Ashton, M Albert, D Chernyshenko, W Wang, S Zhang, M-A Bisotti, M Franchin, CL Hu, R Stamps, T Hesjedal, H Fangohr


Topological insulators: Engineered heterostructures.

Nature materials 16 (2016) 3-4

T Hesjedal, Y Chen


ARPES study of the epitaxially grown topological crystalline insulator SnTe(111)

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 219 (2017) 35-40

Y Zhang, Z Liu, B Zhou, Y Kim, L Yang, H Ryu, C Hwang, Y Chen, Z Hussain, Z-X Shen, S-K Mo


Signature of type-II Weyl semimetal phase in MoTe2.

Nature communications 8 (2017) 13973-

J Jiang, ZK Liu, Y Sun, HF Yang, CR Rajamathi, YP Qi, LX Yang, C Chen, H Peng, C-C Hwang, SZ Sun, S-K Mo, I Vobornik, J Fujii, SSP Parkin, C Felser, BH Yan, YL Chen

Topological Weyl semimetal (TWS), a new state of quantum matter, has sparked enormous research interest recently. Possessing unique Weyl fermions in the bulk and Fermi arcs on the surface, TWSs offer a rare platform for realizing many exotic physical phenomena. TWSs can be classified into type-I that respect Lorentz symmetry and type-II that do not. Here, we directly visualize the electronic structure of MoTe2, a recently proposed type-II TWS. Using angle-resolved photoemission spectroscopy (ARPES), we unravel the unique surface Fermi arcs, in good agreement with our ab initio calculations that have nontrivial topological nature. Our work not only leads to new understandings of the unusual properties discovered in this family of compounds, but also allows for the further exploration of exotic properties and practical applications of type-II TWSs, as well as the interplay between superconductivity (MoTe2 was discovered to be superconducting recently) and their topological order.


Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior

PHYSICAL REVIEW B 95 (2017) ARTN 024404

J Brambleby, PA Goddard, J Singleton, M Jaime, T Lancaster, L Huang, J Wosnitza, CV Topping, KE Carreiro, HE Tran, ZE Manson, JL Manson


Strain and Magnetic Field Induced Spin-Structure Transitions in Multiferroic BiFeO3

ADVANCED MATERIALS 29 (2017) UNSP 1602327

A Agbelele, D Sando, C Toulouse, C Paillard, RD Johnson, R Ruffer, AF Popkov, C Carretero, P Rovillain, J-M Le Breton, B Dkhil, M Cazayous, Y Gallais, M-A Measson, A Sacuto, P Manuel, AK Zvezdin, A Barthelemy, J Juraszek, M Bibes


Coupled commensurate charge density wave and lattice distortion in Na(2)Ti(2)Pn(2)O (Pn = As,Sb) determined by x-ray diffraction and angle-resolved photoemission spectroscopy

PHYSICAL REVIEW B 94 (2016) ARTN 104515

NR Davies, RD Johnson, AJ Princep, LA Gannon, J-Z Ma, T Qian, P Richard, H Li, M Shi, H Nowell, PJ Baker, YG Shi, H Ding, J Luo, YF Guo, AT Boothroyd


Single-gap superconductivity in beta-Bi2Pd

PHYSICAL REVIEW B 93 (2016) ARTN 144502

J Kacmarcik, Z Pribulova, T Samuely, P Szabo, V Cambel, J Soltys, E Herrera, H Suderow, A Correa-Orellana, D Prabhakaran, P Samuely


Magnetic properties of and : Magnetic hysteresis with coercive fields of up to 55 T

Physical Review B 94 (2016)

J Singleton, JW Kim, CV Topping, A Hansen, E-D Mun, S Chikara, I Lakis, S Ghannadzadeh, P Goddard, X Luo, YS Oh, S-W Cheong, VS Zapf


Making hybrid [n]-rotaxanes as supramolecular arrays of molecular electron spin qubits.

Nature communications 7 (2016) 10240-

A Fernandez, J Ferrando-Soria, EM Pineda, F Tuna, IJ Vitorica-Yrezabal, C Knappke, J Ujma, CA Muryn, GA Timco, PE Barran, A Ardavan, REP Winpenny

Quantum information processing (QIP) would require that the individual units involved--qubits--communicate to other qubits while retaining their identity. In many ways this resembles the way supramolecular chemistry brings together individual molecules into interlocked structures, where the assembly has one identity but where the individual components are still recognizable. Here a fully modular supramolecular strategy has been to link hybrid organic-inorganic [2]- and [3]-rotaxanes into still larger [4]-, [5]- and [7]-rotaxanes. The ring components are heterometallic octanuclear [Cr7NiF8(O2C(t)Bu)16](-) coordination cages and the thread components template the formation of the ring about the organic axle, and are further functionalized to act as a ligand, which leads to large supramolecular arrays of these heterometallic rings. As the rings have been proposed as qubits for QIP, the strategy provides a possible route towards scalable molecular electron spin devices for QIP. Double electron-electron resonance experiments demonstrate inter-qubit interactions suitable for mediating two-qubit quantum logic gates.


All-in-all-Out Magnetic Order and Propagating Spin Waves in Sm_{2}Ir_{2}O_{7}.

Physical review letters 117 (2016) 037201-

C Donnerer, MC Rahn, MM Sala, JG Vale, D Pincini, J Strempfer, M Krisch, D Prabhakaran, AT Boothroyd, DF McMorrow

Using resonant magnetic x-ray scattering we address the unresolved nature of the magnetic ground state and the low-energy effective Hamiltonian of Sm_{2}Ir_{2}O_{7}, a prototypical pyrochlore iridate with a finite temperature metal-insulator transition. Through a combination of elastic and inelastic measurements, we show that the magnetic ground state is an all-in-all-out (AIAO) antiferromagnet. The magnon dispersion indicates significant electronic correlations and can be well described by a minimal Hamiltonian that includes Heisenberg exchange [J=27.3(6)  meV] and Dzyaloshinskii-Moriya interactions [D=4.9(3)  meV], which provides a consistent description of the magnetic order and excitations. In establishing that Sm_{2}Ir_{2}O_{7} has the requisite inversion symmetry preserving AIAO magnetic ground state, our results support the notion that pyrochlore iridates may host correlated Weyl semimetals.


Quantum Interference in Graphene Nanoconstrictions.

Nano letters 16 (2016) 4210-4216

P Gehring, H Sadeghi, S Sangtarash, CS Lau, J Liu, A Ardavan, JH Warner, CJ Lambert, GAD Briggs, JA Mol

We report quantum interference effects in the electrical conductance of chemical vapor deposited graphene nanoconstrictions fabricated using feedback controlled electroburning. The observed multimode Fabry-Pérot interferences can be attributed to reflections at potential steps inside the channel. Sharp antiresonance features with a Fano line shape are observed. Theoretical modeling reveals that these Fano resonances are due to localized states inside the constriction, which couple to the delocalized states that also give rise to the Fabry-Pérot interference patterns. This study provides new insight into the interplay between two fundamental forms of quantum interference in graphene nanoconstrictions.


Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.

Chemistry (Weinheim an der Bergstrasse, Germany) 22 (2016) 1779-1788

ML Baker, T Lancaster, A Chiesa, G Amoretti, PJ Baker, C Barker, SJ Blundell, S Carretta, D Collison, HU Güdel, T Guidi, EJL McInnes, JS Möller, H Mutka, J Ollivier, FL Pratt, P Santini, F Tuna, PLW Tregenna-Piggott, IJ Vitorica-Yrezabal, GA Timco, REP Winpenny

The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities.


Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets.

Journal of the American Chemical Society 138 (2016) 2280-2291

LHR Dos Santos, A Lanza, AM Barton, J Brambleby, WJA Blackmore, PA Goddard, F Xiao, RC Williams, T Lancaster, FL Pratt, SJ Blundell, J Singleton, JL Manson, P Macchi

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.


Bimetallic MOFs (H3O)x[Cu(MF6)(pyrazine)2]·(4 - x)H2O (M = V4+, x = 0; M = Ga3+, x = 1): co-existence of ordered and disordered quantum spins in the V4+ system.

Chemical communications (Cambridge, England) 52 (2016) 12653-12656

JL Manson, JA Schlueter, KE Garrett, PA Goddard, T Lancaster, JS Möller, SJ Blundell, AJ Steele, I Franke, FL Pratt, J Singleton, J Bendix, SH Lapidus, M Uhlarz, O Ayala-Valenzuela, RD McDonald, M Gurak, C Baines

The title compounds are bimetallic MOFs containing [Cu(pyz)2]2+ square lattices linked by MF6n- octahedra. In each, only the Cu2+ spins exhibit long-range magnetic order below 3.5 K (M = V4+) and 2.6 K (M = Ga3+). The V4+ spins remain disordered down to 0.5 K.


The magneto-Hall difference and the planar extraordinary Hall balance

AIP ADVANCES 6 (2016) ARTN 045019

SL Zhang, T Hesjedal

Pages