Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resona...Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER~5kBTc,are important for understanding the superconductivity.Here,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned Fe Se.The low-energy spin excitations(E<10 meV)appear mainly at Q=(±1,0)in the superconducting state(T9K)and the nematic state(T90 K),confirming the constant C_(2) rotational symmetry and ruling out the C_(4) mode at E≈3 meV reported in a prior INS study.Moreover,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing symmetry.At slightly higher energy,low-energy spin excitations become highly anisotropic.The full width at half maximum of spin excitations is elongated along the transverse direction.The Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket aroundΓpoint and the electron pockets centered at MX point.展开更多
Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and ...Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and complex.Here,we utilize a cryogenic optical system equipped with a high-spatial-resolution microscope to characterize surface strains in iron-based superconductors using the digital image correlation method.Compared with other methods such as high-resolution x-ray diffraction,strain gauge,and capacitive sensor,digital image correlation offers a non-contact full-field measurement approach,acting as an optical virtual strain gauge that provides high spatial resolution.The results measured on detwinned BaFe_(2)As_(2)are quantitatively consistent with the distortion measured by x-ray diffraction and neutron Larmor diffraction.These findings highlight the potential of cryogenic digital image correlation as an effective and accessible tool for probing the isotropic and anisotropic strains,facilitating applications of uniaxial strain tuning in research of quantum materials.展开更多
The in-plane magnetotransport of detwinned EuFe2As2 single crystal has been investigated.In the antiferromagnetic phase of Eu^2+spins,very different magnetoresistance results are observed upon the change of the extern...The in-plane magnetotransport of detwinned EuFe2As2 single crystal has been investigated.In the antiferromagnetic phase of Eu^2+spins,very different magnetoresistance results are observed upon the change of the external magnetic field direction and the current direction.This could be attributed to the tunable orientation of the Eu^2+spins under magnetic field.Electron scattering by spin fluctuation,superzone boundary effect,and cyclotron motion of charge carriers are used to interpret the observed anomalous magnetoresistance which is measured by using a current along a direction.The remarkable features of magnetoresistance suggest that itinerant electrons strongly couple with the spin configuration of Eu^2+,which has a huge influence on the transport properties of EuFe2As2.展开更多
基金Beijing Normal University was supported by the Fundamental Research Funds for the Central Universitiesthe National Key Projects for Research and Development of China(No.2021YFA1400400)+1 种基金the National Natural Science Foundation of China(Grant Nos.12174029 and 11922402)the neutron beamtimes from J-PARC(Proposal No.2019A0002)。
文摘Antiferromagnetic spin fluctuation is regarded as the leading driving force for electron pairing in high-Tc superconductors.In iron-based superconductors,spin excitations at low energy range,especially the spin-resonance mode at ER~5kBTc,are important for understanding the superconductivity.Here,we use inelastic neutron scattering(INS)to investigate the symmetry and in-plane wave-vector dependence of low-energy spin excitations in uniaxial-strain detwinned Fe Se.The low-energy spin excitations(E<10 meV)appear mainly at Q=(±1,0)in the superconducting state(T9K)and the nematic state(T90 K),confirming the constant C_(2) rotational symmetry and ruling out the C_(4) mode at E≈3 meV reported in a prior INS study.Moreover,our results reveal an isotropic spin resonance in the superconducting state,which is consistent with the s±wave pairing symmetry.At slightly higher energy,low-energy spin excitations become highly anisotropic.The full width at half maximum of spin excitations is elongated along the transverse direction.The Q-space isotropic spin resonance and highly anisotropic low-energy spin excitations could arise from dyz intra-orbital selective Fermi surface nesting between the hole pocket aroundΓpoint and the electron pockets centered at MX point.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1400400)the Fundamental Research Funds for the Central Universities,and the National Natural Science Foundation of China(Grant Nos.12174029 and 11922402).
文摘Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors.However,accurately characterizing anisotropic strain can be challenging and complex.Here,we utilize a cryogenic optical system equipped with a high-spatial-resolution microscope to characterize surface strains in iron-based superconductors using the digital image correlation method.Compared with other methods such as high-resolution x-ray diffraction,strain gauge,and capacitive sensor,digital image correlation offers a non-contact full-field measurement approach,acting as an optical virtual strain gauge that provides high spatial resolution.The results measured on detwinned BaFe_(2)As_(2)are quantitatively consistent with the distortion measured by x-ray diffraction and neutron Larmor diffraction.These findings highlight the potential of cryogenic digital image correlation as an effective and accessible tool for probing the isotropic and anisotropic strains,facilitating applications of uniaxial strain tuning in research of quantum materials.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.2014JJCB27).
文摘The in-plane magnetotransport of detwinned EuFe2As2 single crystal has been investigated.In the antiferromagnetic phase of Eu^2+spins,very different magnetoresistance results are observed upon the change of the external magnetic field direction and the current direction.This could be attributed to the tunable orientation of the Eu^2+spins under magnetic field.Electron scattering by spin fluctuation,superzone boundary effect,and cyclotron motion of charge carriers are used to interpret the observed anomalous magnetoresistance which is measured by using a current along a direction.The remarkable features of magnetoresistance suggest that itinerant electrons strongly couple with the spin configuration of Eu^2+,which has a huge influence on the transport properties of EuFe2As2.
