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arXiv · 2406.12825

Theory of Coulomb driven nematicity in a multi-valley two-dimensional electron gas

Vladimir Calvera·Agnes Valenti·Sebastian D. Huber·Erez Berg·Steven A. Kivelson
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Abstract

The properties of a two-dimensional electron gas (2DEG) in a semiconductor host with two valleys related by an underlying $C_4$ rotational symmetry are studied using Hartree-Fock (HF) and various other many-body approaches. A familiar artifact of the HF approach is a degeneracy between the valley polarized - ``Ising nematic'' - and spin polarized - ferromagnetic - phases, which is inconsistent with recent variational Monte Carlo (VMC) results. Correlation effects, computed either within the random phase approximation (RPA) or the T-matrix approximation, enhance the valley susceptibility relative to the spin susceptibility. Extrapolating the results to finite interaction strength, we find a direct first-order transition from a symmetry-unbroken state to a spin unpolarized Ising nematic fluid with full valley polarization, in qualitative agreement with VMC. The RPA results are also reminiscent of experiments on the corresponding 2DEG in AlAs heterostructures.

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Vladimir Calvera, Agnes Valenti, Sebastian D. Huber, Erez Berg, Steven A. Kivelson. 2024-06-18. Theory of Coulomb driven nematicity in a multi-valley two-dimensional electron gas. https://doi.org/10.1103/physrevb.111.155135

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