Collective excitations in two-dimensional SU( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>N</mml:mi></mml:math> ) Fermi gases with tunable spin

We measure collective excitations of a harmonically trapped two-dimensional (2D) SU(N Fermi gas of ^{173}b confined to a stack of layers formed by a one-dimensional optical lattice. Quadrupole and breathing modes are excited and monitored in the collisionless regime \lvert\ln(k_F a_{2D})\rvert\gg 1with tunable spin. We observe that the quadrupole mode frequency decreases with increasing number of spin components due to the amplification...