How to create a proportional symbol map with sqrt

query.sql

select 
  *, 
  sqrt(pop_max)*50/5972.93897507751 as sqrt_pop 
from 
  populated_places 
where 
  pop_max > 0 
order by pop_max desc

style.css

#layer {
  marker-fill: ramp([sqrt_pop], cartocolor(Sunset), jenks);
  marker-width: [sqrt_pop];
  marker-allow-overlap: true;
  marker-opacity: 0.7;
  marker-line-width: 0;
  marker-comp-op: multiply;
}