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P4 Thermal effects in strongly correlated antiferromagnets

The goal of this project is to explore the lifetimes of the excitations in a number of gapped antiferromagnets as a function of temperature. In the conventional picture of thermal effects in magnetism, the excitations are long-lived at low temperatures and their lifetime decreases with temperature. The explanation is that thermally activated excitations collide with each other incoherently limiting their lifetimes - observed experimentally as a symmetric Lorentzian energy broadening of the lineshape. The concept of thermal decoherence and Lorentzian linewidth broadening does not apply to all magnetic systems, materials with excitations that interact strongly have recently been found to develop distorted lineshapes with increasing temperature e.g. copper nitrate and Sr3Cr2O8, and the lineshape is characteristic of the nature of the correlations. In this project we plan to investigate the thermal development of the lineshape of a range of different magnetic systems, e.g. dimerised systems, Haldane chains, spin ladders etc. Spin echo and inelastic neutron scattering techniques will be used and refined to give high resolution measurements. Alongside the experiment, theory will also be developed to explain and model these new phenomena.

National Partner: Johannes Reuther (HZB and FU Berlin)

International partners: Fabian Essler, John Chalker (Oxford)

PhD student in charge: Ekaterina Klyushina

additional support: Anup Kumar Bera, Nazmul Islam

Publications:

2016:

E.S. Klyushina, A.C. Tiegel, B. Fauseweh, A.T.M.N. Islam, J.T. Park, B. Klemke, A. Honecker, G.S. Uhrig, S.R. Manmana, B. Lake, Magnetic excitations in the S = 1/2 antiferromagnetic-ferromagnetic chain compound BaCu2V2O8 at zero and finite temperature, Phys. Rev. B 93, 241109(R) (2016), open access version: arXiv:1602.06184

Zhe Wang, D. L. Quintero-Castro, S. Zherlitsyn, S. Yasin, Y. Skourski, A. T. M. N. Islam, B. Lake, J. Deisenhofer, A. Loidl, Field-Induced Magnonic Liquid in the 3D Spin-Dimerized Antiferromagnet Sr3Cr2O8, Phys. Rev. Lett. 116, 147201 (2016)

2015:

A.K. Bera, B. Lake, A.T.M.N. Islam, A. Schneidewind, Critical properties of coupled anisotropic Haldane spin chains in a magnetic field, Phys. Rev. B 92, 060412(R) (2015)

2014:

J. Jensen, D.L. Quintero-Castro, A.T.M.N. Islam, K.C. Rule, M. Mansson, B. Lake, Lineshape of the singlet-triplet excitations in the dimer system Sr3Cr2O8 to first order in the high-density 1/z expansion, Phys. Rev. B 89, 134407 (2014)

2013:

A.K. Bera, B. Lake, A.T.M.N. Islam, B. Klemke, E. Faulhaber, J.M. Law, Field-induced magnetic ordering and single-ion anisotropy in the quasi-one-dimensional Haldane chain compound SrNi2V2O8: A single-crystal investigation, Phys. Rev. B 87, 224423 (2013), open access version: arXiv:1310.0221

Zhe Wang, M. Schmidt, A.K. Bera, A.T.M.N. Islam, B. Lake, A. Loidl, J. Deisenhofer, Low-energy magnetic excitations in the quasi-one-dimensional spin-1 chain compound SrNi2V2O8, Phys. Rev. B 87, 104405 (2013), open access version: arXiv:1212.6859

B. Lake, D.A. Tennant, J.S. Caux, T. Barthel, U. Schollwöck, S.E. Nagler, C.D. Frost, Multispinon Continua at Zero and Finite Temperature in a Near-Ideal Heisenberg Chain, Phys. Rev. Lett. 111, 137205 (2013), open access version: arXiv:1307.4071

2012:

D.L. Quintero-Castro, B. Lake, A.T.M.N. Islam, E.M.  Wheeler, C. Balz, M. Mansson, K.C. Rule, S. Gvasaliya, A. Zheludev, Asymmetric Thermal Line Shape Broadening in a Gapped 3D Antiferromagnet: Evidence for Strong Correlations at Finite Temperature, Phys. Rev. Lett. 109, 127206 (2012), open access version: arXiv:1208.5921


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