Observation of the topological surface state in the nonsymmorphic topological insulator KHgSb

PHYSICAL REVIEW B 96 (2017) ARTN 165143

AJ Liang, J Jiang, MX Wang, Y Sun, N Kumar, C Shekhar, C Chen, H Peng, CW Wang, X Xu, HF Yang, ST Cui, GH Hong, Y-Y Xia, S-K Mo, Q Gao, XJ Zhou, LX Yang, C Felser, BH Yan, ZK Liu, YL Chen

Photoemission study of the electronic structure of valence band convergent SnSe

PHYSICAL REVIEW B 96 (2017) ARTN 165118

CW Wang, YYY Xia, Z Tian, J Jiang, BH Li, ST Cui, HF Yang, AJ Liang, XY Zhan, GH Hong, S Liu, C Chen, MX Wang, LX Yang, Z Liu, QX Mi, G Li, JM Xue, ZK Liu, YL Chen

Quasiparticle Breakdown and Spin Hamiltonian of the Frustrated Quantum Pyrochlore Yb_{2}Ti_{2}O_{7} in a Magnetic Field.

Physical review letters 119 (2017) 057203-

JD Thompson, PA McClarty, D Prabhakaran, I Cabrera, T Guidi, R Coldea

The frustrated pyrochlore magnet Yb_{2}Ti_{2}O_{7} has the remarkable property that it orders magnetically but has no propagating magnons over wide regions of the Brillouin zone. Here we use inelastic neutron scattering to follow how the spectrum evolves in cubic-axis magnetic fields. At high fields we observe, in addition to dispersive magnons, a two-magnon continuum, which grows in intensity upon reducing the field and overlaps with the one-magnon states at intermediate fields leading to strong renormalization of the dispersion relations, and magnon decays. Using heat capacity measurements we find that the low- and high-field regions are smoothly connected with no sharp phase transition, with the spin gap increasing monotonically in field. Through fits to an extensive data set of dispersion relations combined with magnetization measurements, we reevaluate the spin Hamiltonian, finding dominant quantum exchange terms, which we propose are responsible for the anomalously strong fluctuations and quasiparticle breakdown effects observed at low fields.

Crystal growth of pyrochlore rare-earth stannates

JOURNAL OF CRYSTAL GROWTH 468 (2017) 335-339

D Prabhakaran, S Wang, AT Boothroyd

Crystal growth of the triangular-lattice antiferromagnet Ba3CoSb2O9

JOURNAL OF CRYSTAL GROWTH 468 (2017) 345-348

D Prabhakaran, AT Boothroyd

Synthesis of Superconductor-Topological Insulator Hybrid Nanoribbon Structures

NANO 12 (2017) ARTN 1750095

P Schonherr, F Zhang, V Srot, P van Aken, T Hesjedal

Direct experimental determination of the topological winding number of skyrmions in Cu2OSeO3.

Nature communications 8 (2017) 14619-

SL Zhang, G van der Laan, T Hesjedal

The mathematical concept of topology has brought about significant advantages that allow for a fundamental understanding of the underlying physics of a system. In magnetism, the topology of spin order manifests itself in the topological winding number which plays a pivotal role for the determination of the emergent properties of a system. However, the direct experimental determination of the topological winding number of a magnetically ordered system remains elusive. Here, we present a direct relationship between the topological winding number of the spin texture and the polarized resonant X-ray scattering process. This relationship provides a one-to-one correspondence between the measured scattering signal and the winding number. We demonstrate that the exact topological quantities of the skyrmion material Cu2OSeO3 can be directly experimentally determined this way. This technique has the potential to be applicable to a wide range of materials, allowing for a direct determination of their topological properties.

Temperature evolution of topological surface states in Bi2Se3 thin films studied using terahertz spectroscopy


VS Kamboj, A Singh, HE Beere, T Hesjedal, CHW Barnes, DA Ritchie

Lifshitz Transitions Induced by Temperature and Surface Doping in Type-II Weyl Semimetal Candidate T-d-WTe2


Q Zhang, Z Liu, Y Sun, H Yang, J Jiang, S-K Mo, Z Hussain, X Qian, L Fu, S Yao, M Lu, C Felser, B Yan, Y Chen, L Yang

Combining microscopic and macroscopic probes to untangle the single-ion anisotropy and exchange energies in an S=1 quantum antiferromagnet

PHYSICAL REVIEW B 95 (2017) ARTN 134435

J Brambleby, JL Manson, PA Goddard, MB Stone, RD Johnson, P Manuel, JA Villa, CM Brown, H Lu, S Chikara, V Zapf, SH Lapidus, R Scatena, P Macchi, Y-S Chen, L-C Wu, J Singleton

Terahertz spectroscopy of anisotropic materials using beams with rotatable polarization.

Scientific reports 7 (2017) 12337-

CDW Mosley, M Failla, D Prabhakaran, J Lloyd-Hughes

We introduce a polarization-resolved terahertz time-domain spectrometer with a broadband (0.3-2.5 THz), rotatable THz polarization state, and which exhibits minimal change in the electric field amplitude and polarization state upon rotation. This was achieved by rotating an interdigitated photoconductive emitter, and by detecting the orthogonal components of the generated THz pulse via electro-optic sampling. The high precision (<0.1°) and accuracy (<1.0°) of this approach is beneficial for the study of anisotropic materials without rotating the sample, which can be impractical, for instance for samples held in a cryostat. The versatility of this method was demonstrated by studying the anisotropic THz optical properties of uniaxial and biaxial oxide crystals. For uniaxial ZnO and LaAlO3, which have minimal THz absorption across the measurement bandwidth, the orientations of the eigenmodes of propagation were conveniently identified as the orientation angles that produced a transmitted THz pulse with zero ellipticity, and the birefringence was quantified. In CuO, a multiferroic with improper ferroelectricity, the anisotropic THz absorption created by an electromagnon was investigated, mapping its selection rule precisely. For this biaxial crystal, which has phonon and electromagnon absorption, the polarization eigenvectors exhibited chromatic dispersion, as a result of the monoclinic crystal structure and the frequency-dependent complex refractive index.

Van der Waals epitaxy between the highly lattice mismatched Cu-doped FeSe and Bi2Te3


A Ghasemi, D Kepaptsoglou, PL Galindo, QM Ramasse, T Hesjedal, VK Lazarov

Spin dynamics in the antiferromagnetic phases of the Dirac metals AMnBi(2) (A = Sr, Ca)

PHYSICAL REVIEW B 95 (2017) ARTN 134405

MC Rahn, AJ Princep, A Piovano, J Kulda, YF Guo, YG Shi, AT Boothroyd

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.

Anisotropic magnetic switching along hard [110]-type axes in Er-doped DyFe2/YFe2 thin films


GBG Stenning, GJ Bowden, G van der Laan, AI Figueroa, P Bencok, P Steadman, T Hesjedal

Magnetic proximity coupling to Cr-doped Sb2Te3 thin films

PHYSICAL REVIEW B 95 (2017) ARTN 224422

LB Duffy, AI Figueroa, L Gladczuk, N-J Steinke, K Kummer, G van der Laan, T Hesjedal

Topological origin of the type-II Dirac fermions in PtSe2


Y Li, Y Xia, SA Ekahana, N Kumar, J Jiang, L Yang, C Chen, C Liu, B Yan, C Felser, G Li, Z Liu, Y Chen

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


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

Topological triplon modes and bound states in a Shastry-Sutherland magnet

NATURE PHYSICS 13 (2017) 736-+

PA McClarty, F Krueger, T Guidi, SF Parker, K Refson, AW Parker, D Prabhakaran, R Coldea

Nontrivial Berry phase and type-II Dirac transport in the layered material PdTe2

PHYSICAL REVIEW B 96 (2017) ARTN 041201

F Fei, X Bo, R Wang, B Wu, J Jiang, D Fu, M Gao, H Zheng, Y Chen, X Wang, H Bu, F Song, X Wan, B Wang, G Wang