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Author: Fecher, Gerhard H. ×

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    Signatures of Sixfold Degenerate Exotic Fermions in a Superconducting Metal PdSb2
    (Weinheim : Wiley-VCH, 2020) Kumar, Nitesh; Yao, Mengyu; Nayak, Jayita; Vergniory, Maia G.; Bannies, Jörn; Wang, Zhijun; Schröter, Niels B.M.; Strocov, Vladimir N.; Müchler, Lukas; Shi, Wujun; Rienks, Emile D.L.; Mañes, J.L.; Shekhar, Chandra; Parkin, Stuart S.P.; Fink, Jörg; Fecher, Gerhard H.; Sun, Yan; Bernevig, B. Andrei; Felser, Claudia
    Multifold degenerate points in the electronic structure of metals lead to exotic behaviors. These range from twofold and fourfold degenerate Weyl and Dirac points, respectively, to sixfold and eightfold degenerate points that are predicted to give rise, under modest magnetic fields or strain, to topological semimetallic behaviors. The present study shows that the nonsymmorphic compound PdSb2 hosts six-component fermions or sextuplets. Using angle-resolved photoemission spectroscopy, crossing points formed by three twofold degenerate parabolic bands are directly observed at the corner of the Brillouin zone. The group theory analysis proves that under weak spin–orbit interaction, a band inversion occurs. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Multiple Dirac cones at the surface of the topological metal LaBi
    (London : Nature Publishing Group, 2017) Nayak, Jayita; Martinsson, Bengt G.; Kumar, Nitesh; Shekhar, Chandra; Singh, Sanjay; Fink, Jörg; Rienks, Emile E.D.; Fecher, Gerhard H.; Parkin, Stuart S.P.; Yan, Binghai; Felser, Claudia
    The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties, including an extremely large and anisotropic magnetoresistance. Experimental evidence for topological surface states is still missing although band inversions have been postulated to induce a topological phase in LaBi. In this work, we have revealed the existence of surface states of LaBi through the observation of three Dirac cones: two coexist at the corners and one appears at the centre of the Brillouin zone, by employing angle-resolved photoemission spectroscopy in conjunction with ab initio calculations. The odd number of surface Dirac cones is a direct consequence of the odd number of band inversions in the bulk band structure, thereby proving that LaBi is a topological, compensated semimetal, which is equivalent to a time-reversal invariant topological insulator. Our findings provide insight into the topological surface states of LaBi’s semi-metallicity and related magneto-transport properties.
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    A New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording
    (Weinheim : Wiley-VCH, 2020) He, Yangkun; Fecher, Gerhard H.; Fu, Chenguang; Pan, Yu; Manna, Kaustuv; Kroder, Johannes; Jha, Ajay; Wang, Xiao; Hu, Zhiwei; Agrestini, Stefano; Herrero-Martín, Javier; Valvidares, Manuel; Skourski, Yurii; Schnelle, Walter; Stamenov, Plamen; Borrmann, Horst; Tjeng, Liu Hao; Schaefer, Rudolf; Parkin, Stuart S.P.; Coey, John Michael D.; Felser, Claudia
    The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2. © 2020 The Authors. Published by Wiley-VCH GmbH