How to express x*2^(1/x)-x in CVX?

x*2^(1/x)-x is convex by verifying its second order deritave. And x > 0 is a scalar. But how to express it in CVX?

For further clarification: whether or not x*2^(1/x) is used in a constraint, use z in place of x*2^(1/x).

Thank you, I will work it out.