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Dive into the research topics where M. D. Watson is active.

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Featured researches published by M. D. Watson.


Physical Review Letters | 2015

Linear magnetoresistance caused by mobility fluctuations in n-doped Cd3As2

Arjun Narayanan; M. D. Watson; S. F. Blake; N. Bruyant; L. Drigo; Yulin Chen; D. Prabhakaran; Binghai Yan; Claudia Felser; Tai Kong; Paul C. Canfield; Amalia I. Coldea

Cd(3)As(2) is a candidate three-dimensional Dirac semimetal which has exceedingly high mobility and nonsaturating linear magnetoresistance that may be relevant for future practical applications. We report magnetotransport and tunnel diode oscillation measurements on Cd(3)As(2), in magnetic fields up to 65 T and temperatures between 1.5 and 300 K. We find that the nonsaturating linear magnetoresistance persists up to 65 T and it is likely caused by disorder effects, as it scales with the high mobility rather than directly linked to Fermi surface changes even when approaching the quantum limit. From the observed quantum oscillations, we determine the bulk three-dimensional Fermi surface having signatures of Dirac behavior with a nontrivial Berry phase shift, very light effective quasiparticle masses, and clear deviations from the band-structure predictions. In very high fields we also detect signatures of large Zeeman spin splitting (g∼16).


New Journal of Physics | 2013

Study of the structural, electric and magnetic properties of Mn-doped Bi2Te3 single crystals

M. D. Watson; L. J. Collins-McIntyre; L. R. Shelford; Amalia I. Coldea; D. Prabhakaran; Susannah Speller; Tayebeh Mousavi; C.R.M. Grovenor; Z. Salman; Sean Giblin; G. van der Laan; T. Hesjedal

Breaking the time reversal symmetry of a topological insulator, for example by the presence of magnetic ions, is a prerequisite for spin-based electronic applications in the future. In this regard Mn-doped Bi2Te3 is a prototypical example that merits a systematic investigation of its magnetic properties. Unfortunately, Mn doping is challenging in many host materials—resulting in structural or chemical inhomogeneities affecting the magnetic properties. Here, we present a systematic study of the structural, magnetic and magnetotransport properties of Mn-doped Bi2Te3 single crystals using complimentary experimental techniques. These materials exhibit a ferromagnetic phase that is very sensitive to the structural details, with TC varying between 9 and 13 K (bulk values) and a saturation moment that reaches 4.4(5) μB per Mn in the ordered phase. Muon spin rotation suggests that the magnetism is homogeneous throughout the sample. Furthermore, torque measurements in fields up to 33 T reveal an easy axis magnetic anisotropy perpendicular to the ab-plane. The electrical transport data show an anomaly around TC that is easily suppressed by an applied magnetic field, and also anisotropic behavior due to the spin-dependent scattering in relation to the alignment of the Mn magnetic moment. Hall measurements on different crystals established that these systems are n-doped with carrier concentrations of ~ 0.5–3.0 × 1020 cm−3. X-ray magnetic circular dichroism (XMCD) at the Mn L2,3 edge at 1.8 K reveals a large spin magnetic moment of 4.3(3) μB/Mn, and a small orbital magnetic moment of 0.18(2) μB/Mn. The results also indicate a ground state of mixed d4–d5–d6 character of a localized electronic nature, similar to the diluted ferromagnetic semiconductor Ga1−xMnxAs. XMCD measurements in a field of 6 T give a transition point at T ≈ 16 K, which is ascribed to short range magnetic order induced by the magnetic field. In the ferromagnetic state the easy direction of magnetization is along the c-axis, in agreement with bulk magnetization measurements. This could lead to gap opening at the Dirac point, providing a means to control the surface electric transport, which is of great importance for applications.


Physical Review Letters | 2013

Quasiparticle Mass Enhancement Close to the Quantum Critical Point in BaFe2(As1-xPx)(2)

P. Walmsley; C. Putzke; L. Malone; I. Guillamon; David Vignolles; Cyril Proust; S. Badoux; Amalia I. Coldea; M. D. Watson; S. Kasahara; Y. Mizukami; T. Shibauchi; Y. Matsuda; Antony Carrington

We report a combined study of the specific heat and de Haas-van Alphen effect in the iron-pnictide superconductor BaFe2(As(1-x)P(x))2. Our data when combined with results for the magnetic penetration depth give compelling evidence for the existence of a quantum critical point close to x=0.30 which affects the majority of the Fermi surface by enhancing the quasiparticle mass. The results show that the sharp peak in the inverse superfluid density seen in this system results from a strong increase in the quasiparticle mass at the quantum critical point.


AIP Advances | 2014

X-ray magnetic spectroscopy of MBE-grown Mn-doped Bi2Se3 thin films

L. J. Collins-McIntyre; M. D. Watson; A. A. Baker; S. L. Zhang; Amalia I. Coldea; S. E. Harrison; Aakash Pushp; A. J. Kellock; Stuart S. P. Parkin; G. van der Laan; T. Hesjedal

We report the growth of Mn-doped Bi2Se3 thin films by molecular beam epitaxy (MBE), investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), SQUID magnetometry and x-ray magnetic circular dichroism (XMCD). Epitaxial films were deposited on c-plane sapphire substrates by co-evaporation. The films exhibit a spiral growth mechanism typical of this material class, as revealed by AFM. The XRD measurements demonstrate a good crystalline structure which is retained upon doping up to ∼7.5 atomic-% Mn, determined by Rutherford backscattering spectrometry (RBS), and show no evidence of the formation of parasitic phases. However an increasing interstitial incorporation of Mn is observed with increasing doping concentration. A magnetic moment of 5.1 μB/Mn is obtained from bulk-sensitive SQUID measurements, and a much lower moment of 1.6 μB/Mn from surface-sensitive XMCD. At ∼2.5 K, XMCD at the Mn L2,3 edge, reveals short-range magnetic order in the films and indicates ferromagnetic order below 1.5 K.


Annual Review of Condensed Matter Physics | 2018

The Key Ingredients of the Electronic Structure of FeSe

Amalia I. Coldea; M. D. Watson

FeSe is a fascinating superconducting material at the frontier of research in condensed matter physics. Here, we provide an overview of 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 among iron-based superconductors, as it is a multiband system exhibiting strong orbitally dependent electronic correlations and unusually small Fermi surfaces and is prone to different electronic instabilities. We pay particular attention to the evolution of the electronic structure that accompanies the tetragonal-orthorhombic structural distortion of the lattice around 90 K, which stabilizes a unique nematic electronic state. Finally, we discuss how the multiband multiorbital nematic electronic structure impacts our understanding of the superconductivity, and show that...


Physical Review Letters | 2012

de Haas-van Alphen Study of the Fermi Surfaces of Superconducting LiFeP and LiFeAs

C. Putzke; Amalia I. Coldea; I. Guillamon; David Vignolles; Alix McCollam; David LeBoeuf; M. D. Watson; I. I. Mazin; S. Kasahara; Takahito Terashima; T. Shibauchi; Y. Matsuda; Antony Carrington

We report a de Haas-van Alphen oscillation study of the 111 iron pnictide superconductors LiFeAs with T(c) ≈ 18 K and LiFeP with T(c) ≈ 5 K. We find that for both compounds the Fermi surface topology is in good agreement with density functional band-structure calculations and has almost nested electron and hole bands. The effective masses generally show significant enhancement, up to ~3 for LiFeP and ~5 for LiFeAs. However, one hole Fermi surface in LiFeP shows a very small enhancement, as compared with its other sheets. This difference probably results from k-dependent coupling to spin fluctuations and may be the origin of the different nodal and nodeless superconducting gap structures in LiFeP and LiFeAs, respectively.


Physical Review B | 2017

Suppression of electronic correlations by chemical pressure from FeSe to FeS

Pascal Reiss; M. D. Watson; T. K. Kim; Amir A. Haghighirad; Daniel N. Woodruff; M. Bruma; Simon J. Clarke; Amalia I. Coldea

In iron-based superconductors, the interplay between nematicity, magnetism, and superconductivity is still not fully understood. Experimentally, the isoelectronic series FeSe


New Journal of Physics | 2017

Electronic anisotropies revealed by detwinned angle-resolved photo-emission spectroscopy measurements of FeSe

M. D. Watson; Amir A. Haghighirad; Luke C. Rhodes; M. Hoesch; T. K. Kim

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Physical Review B | 2015

Fermi surface of IrTe2 in the valence-bond state as determined by quantum oscillations

S.F. Blake; M. D. Watson; Alix McCollam; S. Kasahara; R. D. Johnson; A. Narayanan; Gheorghe L. Pascut; Kristjan Haule; V. Kiryukhin; Toshifumi Yamashita; D. Watanabe; T. Shibauchi; Y. Matsuda; Amalia I. Coldea

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Physical Review B | 2017

Strongly enhanced temperature dependence of the chemical potential in FeSe

Luke C. Rhodes; M. D. Watson; Amir A. Haghighirad; Matthias Eschrig; T. K. Kim

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M. Hoesch

European Synchrotron Radiation Facility

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I. I. Mazin

United States Naval Research Laboratory

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David Vignolles

Centre national de la recherche scientifique

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