0.29Pb(In_(1/2)Nb_(1/2))O_(3)-0.45Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.26PbTiO_(3)single crystals have been studied using tripleaxis based elastic and inelastic neutron scattering.Elastic diffuse scattering reveals the presenc...0.29Pb(In_(1/2)Nb_(1/2))O_(3)-0.45Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.26PbTiO_(3)single crystals have been studied using tripleaxis based elastic and inelastic neutron scattering.Elastic diffuse scattering reveals the presence of polar nano-regions(PNR's)in this system,which emerge at the Burns temperature(TB~630 K)and then grow continuously in population and correlation size down to 100 K.At 300 K,characteristic“butterfly”and ellipsoid shaped diffuse scattering patterns are observed in the HK0 scattering plane.Electrical poling along the[110]direction produces a marked asymmetry in the diffuse scattering patterns,with the parallel-to-the-field components enhanced while the perpendicular-to-the-field components suppressed.Several low-energy phonon branches along the[100]and[110]directions have been measured.Most significantly,the PNR-acoustic phonon coupling is confirmed for the[110]transverse acoustic(TA)phonons polarized along the[1-10]real space direction and the[100]TA phonons.This coupling appears to be anisotropic and correlated with the PNRs'distribution,and also affected by the relative length scales of the PNRs and phonon wave vectors.The well-known“waterfall”phenomenon is observed on the[100]and[110]transverse optical(TO)branches,near the zone center.The optical phonons exhibit a lowest-energy,zone center soft TO mode,whose squared energy increases linearly with decreasing temperature below TB.展开更多
We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves we...We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves were revealed in the ferromagnetic state.Similarly,dispersive but damped spin excitations were found in the paramagnetic state.The effective exchange interactions were estimated using a semi-classical Heisenberg model to consistently reproduce the experimental TCand spin stiffness.However,a full spin wave gap below Eg=2.3 meV was observed at T=4 K.This value was considerably larger than the estimated magnetic anisotropy energy(~0.6 meV),and its temperature dependence indicated a significant contribution from the Weyl fermions.These results suggest that Co3Sn2S2 is a three-dimensional correlated system with a large spin stiffness,and the low-energy spin dynamics can interplay with the topological electron states.展开更多
基金QL,YL,RLWand JW acknowledge the support of the Australian Research Council(ARC)DP160104780 in the form of ARC Discovery Grants.YL also acknowledges support from the ARC Future Fellowships Program.
文摘0.29Pb(In_(1/2)Nb_(1/2))O_(3)-0.45Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.26PbTiO_(3)single crystals have been studied using tripleaxis based elastic and inelastic neutron scattering.Elastic diffuse scattering reveals the presence of polar nano-regions(PNR's)in this system,which emerge at the Burns temperature(TB~630 K)and then grow continuously in population and correlation size down to 100 K.At 300 K,characteristic“butterfly”and ellipsoid shaped diffuse scattering patterns are observed in the HK0 scattering plane.Electrical poling along the[110]direction produces a marked asymmetry in the diffuse scattering patterns,with the parallel-to-the-field components enhanced while the perpendicular-to-the-field components suppressed.Several low-energy phonon branches along the[100]and[110]directions have been measured.Most significantly,the PNR-acoustic phonon coupling is confirmed for the[110]transverse acoustic(TA)phonons polarized along the[1-10]real space direction and the[100]TA phonons.This coupling appears to be anisotropic and correlated with the PNRs'distribution,and also affected by the relative length scales of the PNRs and phonon wave vectors.The well-known“waterfall”phenomenon is observed on the[100]and[110]transverse optical(TO)branches,near the zone center.The optical phonons exhibit a lowest-energy,zone center soft TO mode,whose squared energy increases linearly with decreasing temperature below TB.
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303100,2017YFA0302900,2016YFA0300500,2017YFA0206300,and 2019YFA0704900)the National Natural Science Foundation of China(Grant Nos.11974392,11974394,11822411,51722106,11674372,11774399,11961160699,and 12061130200)+3 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB07020300,XDB25000000,and XDB33000000)the Beijing Natural Science Foundation(Grant Nos.JQ19002,Z180008,and Z190009)support from the Youth Innovation Promotion Association of CAS(Grant Nos.2013002,and 2016004)support from the K.C.Wong Education Foundation(GJTD-2018-01)。
文摘We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves were revealed in the ferromagnetic state.Similarly,dispersive but damped spin excitations were found in the paramagnetic state.The effective exchange interactions were estimated using a semi-classical Heisenberg model to consistently reproduce the experimental TCand spin stiffness.However,a full spin wave gap below Eg=2.3 meV was observed at T=4 K.This value was considerably larger than the estimated magnetic anisotropy energy(~0.6 meV),and its temperature dependence indicated a significant contribution from the Weyl fermions.These results suggest that Co3Sn2S2 is a three-dimensional correlated system with a large spin stiffness,and the low-energy spin dynamics can interplay with the topological electron states.
