Object keeps slowing down for no apparent reason

I’ve created a very simple 3d scene. I have a plane and a cube with a rigidbody. But for some reason, even when I set drag and angular drag to 0, my cube keeps slowing down. I move it using “rigidbody.AddForce”. The cube starts slowing down when I stop adding force. However, when I turn the gravity off, this stops and the cube keeps moving without changing its speed unless I apply another force. It feels like there is friction between the cube and the plane. Do rigidbodies add friction? Any idea why the cube is stopping or how to fix it?

Of course, Unity implements the friction of Rigidbody objects with each other. To remove the friction force, you need to create a physical material and assign it to the object (cube) collider. Here are the parameters of the frictionless physical material:
189259-physicmaterial.png