# Fate of Pomeranchuk effect in ultrahigh magnetic fields

## TL;DR

This paper explores how ultrahigh magnetic fields affect the Pomeranchuk effect, where a substance solidifies when heated, using an electron system as a model.

## Contribution

The study demonstrates the Pomeranchuk effect in an electron system and reveals its reentrant behavior under ultrahigh magnetic fields.

## Key findings

- An electron system exhibits the Pomeranchuk effect, solidifying in a high magnetic field.
- The system shows a reentrant liquid state in ultrahigh magnetic fields.
- Magnetic entropy and magnetisation changes explain the observed behavior.

## Abstract

The Pomeranchuk effect is a counterintuitive phenomenon where liquid helium-3 (3He) solidifies under specific pressures, not when cooled, but when heated. This behaviour originates from the magnetic entropy of nuclear spins, suggesting a magnetic field should influence it. However, its detailed response to magnetic fields remains elusive due to the small nuclear magneton of 3He and lack of analogous fermion systems. Here, we show that an electron system also exhibit the Pomeranchuk effect, where the Fermi liquid state solidifies in a high magnetic field, unlike conventional electron systems where a field melts an electron solid into a metal. Remarkably, the electron system displays a reentrant liquid state in ultrahigh fields. These responses are explained by changes in magnetic entropy and magnetisation, extending the underlying physics to 3He. Our findings clarify magnetic-field impact on the Pomeranchuk effect and open avenues for magnetic control of chemical interactions.

Solidification upon heating, known as Pomeranchuk effect, is a known phenomenon for 3He. Here, leveraging on the hybridization of organic molecules orbitals with those of inorganic elements in polymers, the authors report the Pomeranchuk effect within an electronic system and the impact of magnetic fields on it.