The landlord has to pay the tax whether they're renting it out or not, but what kind of tax you're assessing affects how much they can charge in rent to their tenant.
When you tax something, the cost typically gets "passed on" because you are changing the marginal profitability of that thing, and this causes the supply to decrease, which drives up the price.
We can make more buildings. But we can't make more land (locations).
So theory has long held that a tax on the value of land (also known as a site value tax) cannot be passed on to tenants, because it's not like someone says "well the cost of holding land went up this week Charlie, better make slightly less land this quarter." Though they can and absolutely do in fact do that with regards to, say, housing construction (and gasoline, and cigarettes, and sirloin steaks, and plush dolls, and anything else you might want to tax).
And this is exactly the empirical effect that the referenced research paper (and many more like it) find in practice. If you assign a split-rate property tax which taxes two things: land, and improvements (buildings, essentially) at different rates, and you have a natural experiment where you randomly vary the tax rate on the improvements and the tax rate on the land, you will find that the price of the property goes down proportionately to the tax rate on land (full capitalization of land taxes), but that doesn't happen with the portion of the tax rate that falls on buildings.
See this for more on the underlying theory: https://astralcodexten.substack.com/p/your-book-review-progr...
If you want more sources on the empirical findings I'm happy to provide that to.