Thermodynamic Investigation of Metamagnetism in Pulsed High Magnetic Fields on Heavy Fermion Superconductor UTe₂

Abstract

We investigated the thermodynamic property of the heavy fermion superconductor UTe 2 in pulsed high magnetic fields. The superconducting transition in zero field was observed at T c =1.65 K as a sharp heat capacity jump. Magnetocaloric effect measurements in pulsed-magnetic fields obviously detected a thermodynamic anomaly accompanied by a first-order metamagnetic transition at µ 0 H m =36.0 T when the fields are applied nearly along the hard-magnetization b-axis. From the results of heat capacity measurements in magnetic fields, we found a drastic diverging electronic heat capacity coefficient of the normal state γ N with approaching H m . Comparing with the previous works via the magnetic Clausius-Clapeyron relation, we unveil the thermodynamic details of the metamagnetic transition. The enhancement of the effective mass observed as the development of γ N indicates that quantum fluctuation strongly evolves around H m ; it assists the superconductivity emerging even in extremely high fields.1 arXiv:1907.03033v1 [cond-mat.str-el]

Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2

“…However, in the normal state at 7 T for H a, C e /T does not show a substantial upturn at low temperatures. This result suggests that the normal-state C e /T varies with increasing H, as reported in high-field measurements [27]. Figure 1(b) compares C e (T )/T at 7 T in several field orientations within the ab plane.…”

Comparison of two superconducting phases induced by a magnetic field in UTe2

“…In other compounds, as CeRu 2 Si 2 51 , CeRh 2 Si 2 52 , and URhGe 20 , a T 2 law in ρ(T) was observed down the lowest accessible temperatures at the pressure and/or magnetic-field instabilities. Recently, Fermi-liquid behaviors, including T 2 laws in the electrical resistivity, were reported at the quantum instabilities of UTe 2 under pressure 38 and magnetic field H || b 31,32,34 . In continuity with these studies, fits to the electrical-resistivity data of UTe 2 were done here for all fields investigated in the temperature windows 1.5 ≤ T ≤ 4.2 K for H || b, and 2.2 ≤ T ≤ 4.2 K for H tilted by θ = 27 ± 5°from b to c (see Supplementary Note 1 and Supplementary Fig.…”

Evidence of Fermi surface reconstruction at the metamagnetic transition of the strongly correlated superconductor UTe2

“…Furthermore, reentrant superconductivity arises above H m when the magnetic field is tilted 30 • away from the b axis towards the c axis [10]. The metamagnetic transition occurring at H m with a jump in the magnetization of 0.6 μ B , when the system enters the polarized paramagnetic state (PPM) [10,12,13], is in agreement with a characteristic energy scale given by the temperature of the maximum in the susceptibility of T χ max ≈ 35 K [14] and the maximum of the Hall effect (R H ) [4]. Furthermore, fluctuations are strongly enhanced through H m despite the first-order nature of the metamagnetic transition below the critical end point (CEP) at T CEP ≈ 7 K [12,14].…”