Q. In a certain two-dimensional lattice, the energy dispersion of the electrons is
where 𝑘⃗→ = (𝑘𝑥 , 𝑘𝑦) denotes the wave vector, 𝑎 is the lattice constant and 𝑡 is a constant in units of eV. In this lattice the effective mass tensor 𝑚𝑖𝑗 of electrons calculated at the center of the Brillouin zone has the form
The value of 𝛼 (rounded off to three decimal places) is
Ans: 0.33
