We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assign...We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assigned by the combination of first-principles calculations and the polarization-resolved spectra. Careful symmetry analysis on the angle-dependent spectra demonstrates that the crystal symmetry is strictly described by C_(2h)but can be simplified to D_(3d) with good accuracy. Interestingly, the three compounds share exactly the same lattice structure but show distinct magnetic structures. This provides us with a unique opportunity to study the effect of different magnetic orders on lattice dynamics in MPS_3. Our results reveal that the in-plane Nel antiferromagnetic(AF) order in MnPS_3 favors a spin–phonon coupling compared to the in-plane zig-zag AF in NiPS_3 and FePS_3. We have discussed the mechanism in terms of the folding of magnetic Brillouin zones. Our results provide insights into the relation between lattice dynamics and magnetism in the layered MPX_3(M = transition metal, X = S, Se) family and shed light on the magnetism of monolayer MPX_3 materials.展开更多
We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for la...We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound compared to Ba0.6K0.4Fe2 As2. Similar to Ba0.6K0.4Fe2As2, we observe nearly isotropie superconducting gaps with Fermi surface-dependent magnitudes for Ca0.33Na0.67 Fe2As2. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters.展开更多
基金Project supported by the Ministry of Science and Technology of China(Grant Nos.2016YFA0300504 and 2017YFA0302904)the National Natural Science Foundation of China(Grant Nos.11474357 and 11774419)the Fundamental Research Funds for the Central Universities,China,and the Research Funds of Renmin University of China(Grant No.14XNLQ03)
文摘We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assigned by the combination of first-principles calculations and the polarization-resolved spectra. Careful symmetry analysis on the angle-dependent spectra demonstrates that the crystal symmetry is strictly described by C_(2h)but can be simplified to D_(3d) with good accuracy. Interestingly, the three compounds share exactly the same lattice structure but show distinct magnetic structures. This provides us with a unique opportunity to study the effect of different magnetic orders on lattice dynamics in MPS_3. Our results reveal that the in-plane Nel antiferromagnetic(AF) order in MnPS_3 favors a spin–phonon coupling compared to the in-plane zig-zag AF in NiPS_3 and FePS_3. We have discussed the mechanism in terms of the folding of magnetic Brillouin zones. Our results provide insights into the relation between lattice dynamics and magnetism in the layered MPX_3(M = transition metal, X = S, Se) family and shed light on the magnetism of monolayer MPX_3 materials.
基金Supported by Chinese Academy of Sciences under Grant No 2010YIJB6, the National Basic Research Program of China under Grant Nos 2010CB923000, 2011CBA001000 and 2013CB921703, and the National Natural Science Foundation of China under Grant Nos 11004232, 11050110422, 11234014 and 11274362, and the Sino-Swiss Science and Technology Cooperation under Grant No IZLCZ2 138954. We thank J P Hu for useful discussions. This work was partly performed at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland, and at BESSY, Helmholtz Zentrum, Berlin, Germany.
文摘We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound compared to Ba0.6K0.4Fe2 As2. Similar to Ba0.6K0.4Fe2As2, we observe nearly isotropie superconducting gaps with Fermi surface-dependent magnitudes for Ca0.33Na0.67 Fe2As2. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters.
