New framework clears spin-orbit confusion in solids and unifies physics

Physicists have developed a new theoretical framework that resolves longstanding difficulties in modeling spin-orbit coupling in solids, a phenomenon where an electron’s spin and motion are intertwined. Traditional quantum mechanical tools, particularly the orbital angular momentum operator, fail to accurately describe electron behavior in crystalline solids due to the lack of full rotational symmetry in atomic lattices. The new approach, termed relativistic spin-lattice interaction, bypasses these issues by focusing on how an electron’s spin interacts with the solid’s atomic structure using principles from relativity. This method aligns well with standard descriptions of electrons in crystals and respects the periodic atomic arrangement, overcoming limitations of earlier models. The researchers validated their framework across materials of different dimensionalities—a 3D semiconductor (gallium arsenide), a 2D insulator (hexagonal boron nitride), and a 1D conductor (atomic chains)—demonstrating improved accuracy in predicting spin behavior and reproducing key phenomena such as the Edelstein and spin Hall effects.