iPhone case material for best heat dissipation?

What case material for iPhone is most effective at dissipating heat. With my current case, my iPhone 11 often feels hot at the bottom of the screen but cools down when I take the case off, so I am confident that the case causes some heat to linger around. I was wondering which material will be best at dissipating heat and if you have any recommendations? TPU, rubber, plastic, metal, silicone, etc? *This is not a shopping recommendation question, rather a material specific question.*