  In the magic angle twisted bilayer graphene (MATBG), one of the most
remarkable observations is the $C_3$-symmetry-breaking nematic state. We
identify that the nematicity in MATBG is the $E$-symmetry ferro bond order,
which is the modulation of correlated hopping integrals owing to the
$E$-symmetry particle-hole pairing condensation. The nematicity in MATBG
originates from prominent quantum interference among $SU(4)$ valley+spin
composite fluctuations. This novel "valley + spin fluctuation interference
mechanism" is revealed by the density wave equation analysis for realistic
multiorbital Hubbard model for MATBG. \color{black}We find that the nematic
state is robust once three van Hove singularity points exist in each valley.
This interference mechanism also causes novel time-reversal-symmetry-broken
valley polarization accompanied by a charge loop current. We discuss
interesting similarities and differences between MATBG and Fe-based
superconductors.
