What are the units for effective mass in the formula m* = (h/2pi)2(d2E/dk2)-1?

[magnifik]

Are the units for effective mass in kg? I have been trying to wrap my head around the concept then realized I wasn't even sure about the units.

The formula is: m_* = (h/2pi)²(d²E/dk²)^-1

the units of h are in J-s, and the units of E are in J so...
(J-s)²/J = J-s²
J = kg m²/s²
kg m² s²/s² = kg m²

why am i left with a m² unit??

 

[phyzguy]

k has units of inverse length. You have a k^2 in the numerator, which has units of m^-2, which will cancel the m^2, and leave you with m* having units of kg, which is correct.