Perspective on the muon-spin rotation/relaxation under hydrostatic pressure

TL;DR

This paper reviews the use of muon-spin rotation/relaxation ($$SR) technique under hydrostatic pressure, discussing experimental requirements, facilities, and key results in studying magnetic and superconducting materials.

Contribution

It provides a comprehensive overview of the current state, experimental setup, and recent findings of $$SR under pressure techniques in condensed matter research.

Findings

Overview of $$SR experimental requirements under pressure

Description of the high-pressure muon facility at PSI

Selected experimental results demonstrating $$SR capabilities under pressure

Abstract

Pressure, together with temperature, electric and magnetic fields, alters the system and allows to investigate the fundamental properties of the matter. Under applied pressure the interatomic distances shrink, which modify interactions between atoms and may lead to appearance of a new (sometime exotic) physical properties as, e.g., pressure induced phase transition(s); quantum critical points(s), new structural, magnetic and/or superconducting states; changes of the temperature evolution and the symmetry of the order parameter(s) etc. The muon-spin rotation/relaxation ($\mu$SR) appears to be a commonly used powerful technique allowing to study the magnetic and superconducting responses of various materials under extreme conditions. At present, $\mu$SR experiments might be performed under the high magnetic field up to $\simeq 9$ T, temperatures down to $\simeq 10-15$ mK and hydrostatic pressure up to $\simeq 2.8$ GPa. In the following Perspective paper the requirements to the $\mu$SR under pressure experiments, the existing high-pressure muon facility at the Paul Scherrer Institute (Switzerland), and selected experimental results obtained by using the $\mu$SR under pressure technique are discussed.