What does this equation mean?

Here the paper states its first honest limitation before drawing another line of the device. Every strain-to-tilt sensitivity that goes into the temperature above is computed, not measured — no experiment between 2016 and 2026 reports a tilt parameter under strain in any real type-II material. The most recent attempt is the same Mo _{0.91} W _{0.09} Te _2 operando-strain study the device borrows its material choice from: Lanz and collaborators delivered tensile strain up to 0.34 percent along the crystal’s a-axis, reversible below about 0.17 percent, and measured a roughly 30-percent increase in the density of states at the Fermi level using strain-resolved photoemission — a careful, state-of-the-art measurement of how the bands respond to strain, and one that stops short, by the authors’ own account, of reporting a tilt parameter or locating a type-I/type-II crossing [ 3 ] . The gap is not a matter of a less careful group choosing not to look; it is that nobody has yet built the measurement that isolates the tilt itself from the other things strain does to a band structure.