# Thermodynamic Investigation of Metamagnetism in Pulsed High Magnetic Fields on Heavy Fermion Superconductor UTe$_2$

## TL;DR

This study explores the thermodynamic behavior of the heavy fermion superconductor UTe$_2$ under pulsed high magnetic fields, revealing a first-order metamagnetic transition and significant electronic mass enhancement near the transition.

## Contribution

It provides new thermodynamic insights into the metamagnetic transition and quantum fluctuations in UTe$_2$ under high magnetic fields, which were not previously characterized in detail.

## Key findings

- Detection of a first-order metamagnetic transition at 36 T.
- Diverging electronic heat capacity coefficient near the transition.
- Quantum fluctuations enhance superconductivity at high fields.

## 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 $T_{\rm c}$=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 $\mu$$_{0}$$H_{\rm 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 $\gamma$$_{\rm N}$ with approaching $H_{\rm m}$. 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 $\gamma_{\rm N}$ indicates that quantum fluctuation strongly evolves around $H_{\rm m}$; it assists the superconductivity emerging even in extremely high fields.