The discovery of pressure-induced superconductivity in helimagnets(CrAs,MnP)has attracted considerable interest in understanding the relationship between complex magnetism and unconventional superconductivity.However,the nature of the magnetism and magnetic interactions that drive the unusual double-helical magnetic order in these materials remains unclear.Here,we report neutron scattering measurements of magnetic excitations in CrAs single crystals at ambient pressure.Our experiments reveal well defined spin wave excitations up to about 150 meV with a pseudogap below 7 meV,which can be effectively described by the Heisenberg model with nearest neighbor exchange interactions.Most surprisingly,the spin excitations are largely quenched above the Néel temperature,in contrast to cuprates and iron pnictides where the spectral weight is mostly preserved in the paramagnetic state.Our results suggest that the helimagnetic order is driven by strongly frustrated exchange interactions,and that CrAs is at the verge of itinerant and correlation-induced localized states,which is therefore highly pressure-tunable and favorable for superconductivity.

Yayuan Qin;Yao Shen;Yiqing Hao;Hongliang Wo;Shoudong Shen;Russell A.Ewings;Yang Zhao;Leland W.Harriger;Jeffrey W.Lynn;Jun Zhao

State Key Laboratory of Surface Physics and Department of Physics,Fudan University,Shanghai 200433,China;Shanghai Qizhi Institute,Shanghai 200232,China;ISIS Pulsed Neutron and Muon Source,STFC Rutherford Appleton Laboratory,Harwell Campus,Didcot,Oxon,OX110QX,United Kingdom;NIST Center for Neutron Research,National Institute of Standards and Technology,Gaithersburg,MD 20899,USA;Department of Materials Science and Engineering,University of Maryland,College Park,MD 20742,USA;Institute of Nanoelectronics and Quantum Computing,Fudan University,Shanghai 200433,China;Shanghai Research Center for Quantum Sciences,Shanghai 201315,China

中国物理快报（英文版）

[1]Yayuan Qin;Yao Shen;Yiqing Hao;Hongliang Wo;Shoudong Shen;Russell A.Ewings;Yang Zhao;Leland W.Harriger;Jeffrey W.Lynn;Jun Zhao-.Frustrated Magnetic Interactions and Quenched Spin Fluctuations in CrAs)[J].中国物理快报（英文版）,2022(12):93-97

Frustrated,CrAs,helimagnets,cuprates,pnictides,helimagnetic

Magnetic,Interactions,Quenched,Spin,Fluctuations,discovery,pressure,induced,superconductivity,MnP,has,attracted,considerable,interest,understanding,relationship,between,complex,magnetism,unconventional,However,nature,interactions,that,unusual,double,helical,order,these,materials,remains,unclear,Here,report,neutron,scattering,measurements,excitations,single,crystals,ambient,Our,experiments,reveal,well,defined,spin,wave,about,meV,pseudogap,below,which,can,effectively,described,by,Heisenberg,model,nearest,neighbor,exchange,Most,surprisingly,largely,quenched,above,temperature,contrast,iron,where,spectral,weight,mostly,preserved,paramagnetic,results,suggest,driven,strongly,frustrated,verge,itinerant,correlation,localized,states,therefore,highly,tunable,favorable

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