ESRF News June 2024

June 2024 ESRFnews

HIGH-PRESSURE SUPERCONDUCTIVITY

of magnetism. In this way, Eremets and colleagues

could unambiguously demonstrate the expulsion of

the magnetic field by the surrounding H

S when it

reached a relatively high temperature, and thereby

prove its superconductivity beyond doubt (Science

351 6279). The experiment is difficult to perform, but

with the completed three-year transfer and upgrade

of the Mössbauer beamline to the ESRF’s ID14 port,

scientists have the benefit of an order-of-magnitude

resolution boost, from 10

μm to 0.8 μm. “Now, instead

of studying the entire sample in integral, one can

map a sample, giving a two-dimensional profile of a

superconducting state,” says Alexander Chumakov, the

scientist in charge of ID14.

Mössbauer spectroscopy is not the only way to

study magnetism within DACs In the past few years

groups led by JeanFrançois Roch and Paul Loubeyre

at the Université ParisSaclay in France and others have

been developing a method that exploits a defect in

diamonds known as the nitrogen vacancy NV centre

The ability of an NV to fluoresce in a microwave field

is dependent on its spin the energy of which in turn

depends on an external magnetic field Therefore

performing microwave spectroscopy at a diamond

anvil tip within a DAC allows the mapping of the

contained samples magnetism

In 2020 Loubeyre and colleagues demonstrated that

a compact NV magnetic microscope could be installed

on an XRD platform at the SOLEIL synchrotron in

France. Now that ID27 is up and running, he plans

to bring the system to the ESRF, to have the best in

structure and magnetism detection in supercon-

ducting hydride research. “Both techniques have a

similar micrometre space resolution,” he says.

So far, all the superconducting hydrides invest-

igated experimentally stabilise at high pressures, up

to around 300 GPa, which is more or less the squeeze

present at the centre of the Earth. Naturally, such

pressures rule out practical applications, whatever

the transition temperature. For that reason, much of

the new focus is on compounds of hydrogen with

more than one other element – so-called ternary or

quaternary hydrides. Indeed, some of the very first

studies of ternary hydrides have been performed

at the ESRF The hope is that we can obtain a

superhydride superconductor that is metastable

at ambient pressure says Loubeyre A few have

already been predicted by ab initio calculations

Of course all synchrotrons can perform

measurements at high pressures and temperatures

says Garbarino But here at the ESRF with the

machine the new beamlines the new detectors

and the onhand sample environments were in a

privileged situation 

Jon Cartwright

Anna Pakhomova,

beamline scientist

at ID27, helps

users to prepare

high-pressure

superconductivity

experiments.

E S R F