Heavy holographic exotics: Tetraquarks as Efimov states

We provide a holographic description of nonstrange multiquark exotics as compact topological molecules by binding heavy-light mesons to a tunneling configuration in D8-D8 that is homotopic to the vacuum state with a fixed Chern-Simons number. In the tunneling process, the heavy-light mesons transmute to fermions. Their binding is generic and arises from a trade-off between the dipole attraction induced by the Chern-Simons term and the U(1) fermionic repulsion. In the heavy quark limit, the open-flavor tetraquark exotics QQqq and QQqq emerge as bound Efimov states in a degenerate multiplet IJπ=(00+,01+) with opposite intrinsic Chern-Simons numbers ±12. The hidden-flavor tetraquark exotics such as QQqq, QQQq, and QQQQ as compact topological molecules are unbound. Other exotics are also discussed.