How to detect if player stops moving along Y axis

Hey, I am trying to figure out how to detect when the player has 0 velocity along the y axis only (eg. they land on a platform), and then destroy the player. So far I have only been able to find scripts that detect all player movement, but I really need it to just detect the Y axis specifically. Thanks for the help!

Rigidbody rb;

private void Awake(){
    rb = GetComponent<Rigidbody>();
}

private void Update(){
   if(rb.velocity.y < 0){
        // do your code
    }
}