面内扭矩测量法检测CeCoIn $_5$的配对对称性
Pairing Symmetry of CeCoIn$_5$ Detected by In-plane Torque Measurements
摘要：
在$T$温度范围为1.8 K $\leq T \leq 10$ K，外加磁场$H$高达14 T的条件下，对重费米子CeCoIn $_5$单晶进行了面内扭矩测量.正常状态扭矩由$τ_n \propto H^4(1+T/T_K)^{-1}\sin 4ϕ$给出。在减去相应的正常状态扭矩之后获得的混合状态扭矩的可逆部分也显示出四重对称性。此外，在$π/$ 4，3 $π$ /4，5 $π$/4，7 $π$ /4等角度处的不可逆转矩中存在尖峰。可逆转矩中的四重对称性和混合态不可逆转矩中的尖峰都意味着超导序参量的$d_{xy}$对称性。场和温度依赖的可逆混合态扭矩提供了进一步的证据$d_{xy}$波对称性。正常态的四重对称性有不同的起源，因为它与混合态的四重对称性相比具有不同的场和温度依赖性。讨论了正常态四重对称性的可能原因。
英文摘要：
In-plane torque measurements were performed on heavy fermion CeCoIn$_5$ single crystals in the temperature $T$ range 1.8 K $\leq T \leq 10$ K and applied magnetic field $H$ up to 14 T. The normal-state torque is given by $τ_n \propto H^4(1+T/T_K)^{-1}\sin 4ϕ$. The reversible part of the mixed-state torque, obtained after subtracting the corresponding normal state torque, shows also a four-fold symmetry. In addition, sharp peaks are present in the irreversible torque at angles of $π/$4, 3$π$/4, 5$π$/4, 7$π$/4, etc. Both the four-fold symmetry in the reversible torque and the sharp peaks in the irreversible torque of the mixed state imply $d_{xy}$ symmetry of the superconducting order parameter. The field and temperature dependences of the reversible mixed-state torque provide further evidence for $d_{xy}$ wave symmetry. The four-fold symmetry in the normal state has a different origin since it has different field and temperature dependences than the one in the mixed state. The possible reasons of the normal state four-fold symmetry are discussed.
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