It has been suggested that there is possibly a class of stellar-mass black holes (BHs) residing near (distance < 1e3 M ) the galactic center massive black hole, Sgr A*. Possible formation scenarios include the mass segregation of massive stellar-mass black holes and/or the disk migration if there was an active accretion flow near Sgr A* within ~1e7 yr.

In this talk, I will first review the current understanding of EMRI formation channels, then discuss the possibility of detecting Sgr A* with spaceborne GW detectors and its scientific potential in constraining axion dark matter around Sgr A*.