  Recent progresses in condensed matter physics, such as graphene, topological
insulator and Weyl semimetal, often origin from the specific topological
symmetries of their lattice structures. Quantum states with different degrees
of freedom, e.g. spin, valley, layer, etc., arise from these symmetries, and
the coherent superpositions of these states form multiple energy subbands. The
pseudospin, a concept analogy to the Dirac spinor matrices, is a successful
description of such multi-subband systems. When the electron-electron
interaction dominates, many-body quantum phases arise. They usually have
digitized pseudospin polarizations and exhibit sharp phase transitions at
certain universal critical pseudospin energy splittings. In this manuscript, we
present our remarkable discovery of hydrostatic pressure induced degeneracy
between the two lowest Landau levels. This degeneracy is evidenced by the
pseudospin polarization transitions of the fragile correlated quantum liquid
phases near Landau level filling factor $\nu$ = 3/2. Benefitted from the
constant hole concentration and the sensitive nature of these transitions, we
can study the fine-tuning effect of the hydrostatic pressure of the order of 10
$\mu$eV, well beyond the meV-level state-of-the-art resolution of other
techniques.
