When I started this, I was like “that’s like asking if sound waves exhibit wave-particle duality” but by the end I was … less certain. https://bigthink.com/starts-with-a-bang/gravitational-waves-wave-particle-duality/
So - you're looking for "phonons", but you can't draw too many parallels between them and photons because they're different. For example, in a phonon frequency is quantized, not amplitude, and the exact properties depend on the medium. And the technical answer to your question is "kinda, sorta, it depends on who you ask and how you define things and about 70 other things". Emergent properties are like that.
"Actually a thing"? Is the number three a thing? Is "happiness" a thing? Is "DarkUncle" actually a thing and not just a carefully arranged glob of molecules running a program in an organic computer? Yes - phonons are a thing, but they don't really exist independently of the medium they're in. As for different media - waffle waffle, because they say "in a solid" an awful lot, implying the rules are different in a liquid or gas, but i suspect some parts carry over and others don't, and although I expect to get yelled at, this is not really what I'd call a "hard science" from a mechanical engineering point of view - it's more a "hey look this weird phenomena we see in waves and light shows up here too, but doesn't work exactly the same" which is why I caution making a logical leap with gravitational waves also being quantized. Again - I'm a very old school empiricist, if you don't have actual experimental evidence, so far as I'm concerned it's idle speculation. And a thousand string theorists would now write me a sternly worded response, if they saw this. /shrug
@Biggles I guess a better way to think of it is that photons are recognized as elementary particles independent of the medium they propagate through (like electrons). Phonons are different, but I’m not sure in what ways and to what extent.
We enter into a world where normal english isn't precise enough to say things, but...
What is a photon supposed to propagate thru if not for the space they exist in? Does it even make sense to talk about a photon (or anything!) existing independent of the space-time they are existing in? I do grant that a photon appears to be a (here's the shortcomings) "thing" while a phonon is less a "thing" and more a collective behavior of many things - but don't be so sure that the photon on a deeper level isn't really also a collective behavior of many things "underneath" it (a sea of fields). Don't ask for more than that - I don't have the math or real high end physics background, but I can point you to some pretty good youtube videos. Point being - if you take *anything* and look at it too closely, it stops being that thing and becomes sub-things. And if you reach the end like "and that's made of quarks, period, end of story" - you have merely reached the end of our ability to dig deeper (MAYBE!) as opposed to having found the deepest level. It works the same going the other way - it turns out galaxies are part of galaxy clusters which are part of larger web-like structures and so on. Is a "galaxy" a thing? or a collection of things? "Thing"ness is a tricky concept if you look to closely at it.
I would add that normal human experiences and intuition *entirely fail* when you are looking at the very small - but also the very large, the very fast, and very long and short time scales. We desperately want to make new things fit into a box and be "like" something we already know, so we can make analogies and predictions. It's a trap. That's why science is verified by experiment - because much of the time you simply can't extend normal experience to those realms.
@Biggles this was a good conversation
@Biggles it's the difference between a phonon propagating through a medium (air - sound is compression waves of air) and photons propagating through a vacuum
@Biggles photons are an actual recognized particle though, part of the standard model; are phonons even actually a thing?? (And would they be the same thing when sound waves occur in different media - e.g., air vs water?)