<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Q</mml:mi><mml:mi>Q</mml:mi><mml:mover accent="true"><mml:mi>q</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover><mml:mover accent="true"><mml:mi>q</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:math> potential in string models

We propose a string theory construction for the system of two heavy quarks and light antiquarks. The potential is function separation between quarks. define critical distance below which can be thought mainly as compact tetraquark. results show universality tension factorization at small separations expected from quark-diquark symmetry. Our estimate screening length in range lattice QCD. also make comparison with $QQq$ system. potentials look very similar quark but larger they differ. reason this that flattening happens well-separated scales follows different mechanisms: breaking by junction annihilation $QQ\overline{q}\overline{q}$. Moreover, applied to $\overline{Q}\overline{Q}qq$