Multiband superconductivity in Lu3Os4Ge13

Abstract

Intermetallic R3T4X13 series consist of a cage-like structure and have attracted attention due to their unconventional electronic ground states. In this work, we report the normal and superconducting state properties of a high-quality single crystal of Lu3Os4Ge13. Lu3Os4Ge13 belongs to the above-mentioned series and crystallizes in a cubic crystal structure with the space group Using electrical transport, magnetization and heat capacity measurements, we show that Lu3Os4Ge13 is a type-II multi-band superconductor (Tc = 3.1 K) with unusual superconducting properties. The analysis of the low-temperature heat capacity data suggests that Lu3Os4Ge13 is a moderately coupled multi-band BCS superconductor with two gaps () in the superconducting state. The dc-magnetization (M−H) shows a large reversible region in the superconducting state similar to the vortex liquid phase observed in high-Tc superconductors. The value of the Ginzburg number Gi suggests that the thermal fluctuations, though small compared to those in high-Tc cuprates, may play an important role in the unpinning of the vortices in this compound. The electronic band structure calculations show that three bands cross the Fermi level and constitute a complex Fermi surface in Lu3Os4Ge13.