1Recent discovery of both gapped and gapless topological phases in weakly correlated electron systems has introduced various relativistic particles and a number of exotic phenomena in condensed matter physics [1][2][3][4][5] . The Weyl fermion 6-8 is a prominent example of three dimensional (3D), gapless topological excitation, which has been experimentally identified in inversion symmetry breaking semimetals 4,5 . However, their realization in spontaneously time reversal symmetry (TRS) breaking magnetically ordered states of correlated materials has so far remained hypothetical 7, 9, 10 . Here, we report a set of experimental evidence for elusive magnetic Weyl fermions in Mn 3 Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect even at room temperature 11 . Detailed comparison between our angle resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Moreover, our transport measurements have unveiled strong evidence for the chiral anomaly of Weyl fermions, namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. The magnetic Weyl fermions of Mn 3 Sn have a significant technological potential, since a weak field (∼ 10 mT) is adequate for controlling the distribution of Weyl points and the large fictitious field (∼ a few 100 T) in the momentum space. Our discovery thus lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems.Traditionally, topological properties have been considered for the systems supporting gapped bulk excitations 1 . However, over the past few years three dimensional gapless systems such asWeyl and Dirac semimetals have been discovered, which combine two seemingly disjoint notions 2 of gapless bulk excitations and band topology [2][3][4][5] . In 3D inversion or TRS breaking systems, two nondegenerate energy bands can linearly touch at pairs of isolated points in the momentum (k) space, giving rise to the Weyl quasiparticles. The touching points or Weyl nodes act as the unit strength (anti) monopoles of underlying Berry curvature [4][5][6][7] , leading to the protected zero energy surface states also known as the Fermi-arcs 4,5,7 , and many exotic bulk properties such as large anomalous Hall effect (AHE) 12 , optical gyrotropy 13 , and chiral anomaly 6,[14][15][16][17][18][19] . Interestingly, the Weyl fermions can describe low energy excitations of both weakly and strongly correlated electron systems. In weakly correlated, inversion symmetry breaking materials, where the symmetry breaking is entirely caused by the crystal structure rather than the collective properties of electrons, the ARPES has provided evidence for long-lived bulk Weyl fermions and the surface Fermi arcs 4, 5 .On the other hand, the magnetic Weyl fermions have been predicted for several...

The physical properties of lightly doped semiconductors are well described by electronic band-structure calculations and impurity energy levels. Such properties form the basis of present-day semiconductor technology. If the doping concentration n exceeds a critical value n(c), the system passes through an insulator-to-metal transition and exhibits metallic behaviour; this is widely accepted to occur as a consequence of the impurity levels merging to form energy bands. However, the electronic structure of semiconductors doped beyond n(c) have not been explored in detail. Therefore, the recent observation of superconductivity emerging near the insulator-to-metal transition in heavily boron-doped diamond has stimulated a discussion on the fundamental origin of the metallic states responsible for the superconductivity. Two approaches have been adopted for describing this metallic state: the introduction of charge carriers into either the impurity bands or the intrinsic diamond bands. Here we show experimentally that the doping-dependent occupied electronic structures are consistent with the diamond bands, indicating that holes in the diamond bands play an essential part in determining the metallic nature of the heavily boron-doped diamond superconductor. This supports the diamond band approach and related predictions, including the possibility of achieving dopant-induced superconductivity in silicon and germanium. It should also provide a foundation for the possible development of diamond-based devices.

Inspired by the present experimental status of charmed-strange mesons, we perform a systematic study of the charmed-strange meson family in which we calculate the mass spectra of the charmed-strange meson family by taking a screening effect into account in the Godfrey-Isgur model and investigate the corresponding strong decays via the quark pair creation model. These phenomenological analyses of charmed-strange mesons not only shed light on the features of the observed charmed-strange states, but also provide important information on future experimental search for the missing higher radial and orbital excitations in the charmed-strange meson family, which will be a valuable task in LHCb, the forthcoming Belle H, and PANDA. SONG et al. PHYSICAL REVIEW D 91, 054031 (2015)TABLE I. Experimental information of the observed charmed-strange states. State Mass (MeV) [1] Width (MeV) [1] First observation Observed decay modes D, 1968.49 ±0.33 o ; 2112.3 ±0.5 <1.9 D*A 2317) 2317.8 ± 0.6 <3.8 BABAR [3] D+/r° [3] 0,1(2460) 2459.6 ± 0.6 <3.5 CLEO [4] D*+n° [4] 0,1 (2536) 2535.12 ±0.13 0.92 ± 0.05 ITEP, SERP [23] D*+r P3] 0 : 2(2573) 2571.9 ±0.8 16+| ± 3 [24] CLEO [24] D°K+ [24] DtA2632)" 2632.5 ± 1.7 ± 5 .0 [25] < 17 [25] SELEX [25] D°K+ [25] 0*1 (2700) 2688 ± 4 ± 3 [26] 112 ± 7 ± 3 6 [26] BABAR [26] DK [26] 2708 ± 9+1(( [27] 108 ± 23+|f [27] Belle [27] D°K+ [27] 2710 ± 2f)2 [28] 149 ± 7+52 t28] BABAR [28] D^K [28] 2709.2 ± 1.9 ± 4.5 [29] 115.8 ± 7.3 ± 12.1 [29] LHCb [29] DK [29] O[./(2860) 2856.6 ± 1.5 ± 5 .0 [26] 47 ± 7 ± 10 [26] BABAR [26] DK [26] 2862 ± 2±f [28] 48 ± 3 ± 6 [28] BABAR [28] D^K [28] 2866.1 ± 1.0 ±6.3 [29] 69.9 ± 3.2 ± 6.6 [29] LHCb [29] DK [29] 0 ; 3(2860) 2860.5 ± 2.6 ± 2.5 ± 6.0 [30,31] 53 ± 7 ± 4 ± 6 [30,31] LHCb [30,31] D°K~ [30,31] OJi (2860) 2859 ± 12 ± 6 ± 23 [30,31] 159 ± 2 3 ± 2 7 ± 7 2 [30,31] LHCb [30,31] D°K-[30,31] 0.5/(3040) 3044 ± 8l5 30 [28] 239 ± 3 5^2 6 [28]