Implications of Tc variation in UBe13 for a possible Fulde-Ferrell-Larkin-Ovchinnikov phase

TL;DR

This study investigates the heat capacity and critical field behavior of UBe13 with low Tc, providing evidence for a possible FFLO phase indicated by an upturn in Hc2(T) and its proportionality to Tc.

Contribution

It presents experimental evidence linking Tc variation in UBe13 to the potential existence of an FFLO phase, highlighting the role of strong coupling effects.

Findings

Upturn in Hc2(T) below Tc/2 observed

Hc2(0) proportional to Tc(H=0)

Supports FFLO phase hypothesis in UBe13

Abstract

We measure the heat capacity of UBe13 with an unusually low Tc for a polycrystal. We find an upturn in the upper critical field Hc2(T) below about Tc/2, much as for higher-Tc samples. Comparing the critical fields in our sample and in samples with higher Tc's shows that the low-temperature limit of Hc2 is proportional to Tc(H=0), as expected if the upturn comes from an FFLO phase and strong coupling.