Abstract
In spite of its ubiquity in strongly correlated systems, the competition of paired and nematic ground states remains poorly understood. Recently such a competition was reported in the two-dimensional electron gas at filling factor ν = 5/2. At this filling factor a pressure-induced quantum phase transition was observed from the paired fractional quantum Hall state to the quantum Hall nematic. Here we show that the pressure-induced paired-to-nematic transition also develops at ν = 7/2, demonstrating therefore this transition in both spin branches of the second orbital Landau level. However, we find that pressure is not the only parameter controlling this transition. Indeed, ground states consistent with those observed under pressure also develop in a sample measured at ambient pressure, but in which the electron–electron interaction was tuned close to its value at the quantum critical point. Our experiments suggest that electron–electron interactions play a critical role in driving the paired-to-nematic transition.
Highlights
In spite of its ubiquity in strongly correlated systems, the competition of paired and nematic ground states remains poorly understood
We show that ground states consistent with those at high pressures develop in a sample at ambient pressure, but in which the electron–electron interaction is engineered to be close to its critical value
In our earlier work we argued that the simplest explanation for the sequence of the phases and of the stability diagram at ν = 5/2 is the existence of two quantum phase transitions in the limit of T = 0: one from a paired fractional quantum Hall states (FQHSs) to the nematic occurring at Pc, and another from the nematic to an isotropic Fermi fluid at P~c29,35
Summary
In spite of its ubiquity in strongly correlated systems, the competition of paired and nematic ground states remains poorly understood. At a given orbital quantum number, the ordered ground state at half-filled Landau level is either the nematic or the FQHS, but a transition between them did not seem possible in the absence of a symmetry breaking field favoring the nematic.
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