Different behavior of upper critical field in Fe_1-xSe single crystals

【摘要】 The temperature dependences of upper critical field(H_c2) for a series of iron-deficient Fe_1-xSe single crystals are obtained from the measurements of in-plane resistivity in magnetic fields up to 9 T and perpendicular to the ab plane. For the samples with lower superconducting transition temperature T_c（< 7.2 K）, the temperature dependence of H_c2 is appropriately described by an effective two-band model. For the samples with higher T_c（ 7.2 K）, the temperature dependence can also be fitted by a single-band Werthamer–Helfand–Hohenberg formula, besides the two-band model. Such a Tc-dependent change in H_c2（T） behavior is discussed in connection with recent related experimental results, showing an inherent link between the changes of intrinsic superconducting and normal state properties in the Fe Se system.更多还原

【Abstract】 The temperature dependences of upper critical field(H_c2) for a series of iron-deficient Fe_1-xSe single crystals are obtained from the measurements of in-plane resistivity in magnetic fields up to 9 T and perpendicular to the ab plane. For the samples with lower superconducting transition temperature T_c（< 7.2 K）, the temperature dependence of H_c2 is appropriately described by an effective two-band model. For the samples with higher T_c（ 7.2 K）, the temperature dependence can also be fitted by a single-band Werthamer–Helfand–Hohenberg formula, besides the two-band model. Such a Tc-dependent change in H_c2（T） behavior is discussed in connection with recent related experimental results, showing an inherent link between the changes of intrinsic superconducting and normal state properties in the Fe Se system.更多还原