In a certain two-dimensional lattice, the energy dispersion of the electrons is

Q. In a certain two-dimensional lattice, the energy dispersion of the electrons is

where 𝑘⃗→ = (𝑘_𝑥 , 𝑘_𝑦) 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 𝑚_𝑖𝑗 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