My professor briefly mentioned a method of cooling down atoms by subjecting them to a potential which is then repeatedly truncated.
He explained something along these lines: say we have $N_0$ atoms trapped in a potential given by $U=0.5mw^2(x^2+y^2+z^2)$, initially in thermal equilibrium, so at some defined temperature $T_0$.
He said we can cool down the atoms by repeatedly "truncating" the potential, i.e at each truncation, during a time period $\Delta t$ we the potential "becomes constant at a height of $\lambda Tk_B$" (not sure what this means, but I guess he means for points $(x,y,z)$ such that $U(x,y,z) \ge \lambda Tk_B$, after truncation we have $U(x,y,z)=\lambda Tk_B$).
His explanation was just in passing, so I'm wondering if there is a name for this technique of cooling down atoms and how it works. Please discuss the relevant physics involved so I can study quantitatively how this works myself.