Negative Pressure of Anisotropic Compressible Hall States : Implication to Metrology

Pressure, compressibility, and Hall conductance of anisotropic states at higher Landau levels are computed. Pressure and compressibility become negative. Hall conductance is unquantized and varies with filling factor. These facts agree with the recent experimental observations of highly anisotropic compressible states at higher Landau levels. It is shown, as an implication of negative pressure, that the quantum Hall effect has extraordinary stability, that is, Hall resistance is quantized even when the longitudinal resistance does not vanish.