link to study https://pubs.aip.org/aip/apl/article-abstract/127/14/143902/3366312/A-ultra-high-temperature-free-piston?redirectedFrom=fulltext

Why hestpumps? I remember seeing a video of a fresnel lens melting rock to lava. That has to be easier and higher temp than 270.

You already can. Use sunlight to generate electricity to power a laser. Blah blah "not economically viable" that's a skill issue. /s

https://archive.ph/UxDfs

For over a century, the dream of efficiently concentrating low-grade heat into high-temperature industrial energy has been constrained by a stubborn ceiling: 200 degrees Celsius (392 degrees Fahrenheit).
Now, a team from China has shattered that temperature limit. Using a revolutionary heat pump with no moving parts, they achieved an output of 270 degrees with a 145-degree heat source to drive the cycle.

...so a modest but significant improvement has been achieved, but nowhere near the temps required for melting ore.

But maaaaybe, theoretically, with materials and technologies not yet developed, possibly by 2040:

In a December 5 article in Nature Energy, Luo summarised various research fronts, including his team’s thermoacoustic Stirling heat pump, as promising pathways towards the realisation of ultra-high-temperature heat pumps.
He also suggested development directions for materials and technologies needed for future ultra-high-temperature heat pumps operating from 600K to 1,600K, or 327 degrees to 1,327 degrees, saying these could be achieved by 2040.