Steven Kivelson – Stanford University
Wednesday, November 12th, 2025
Zoom opens: 10:30AM EST
Seminar begins: 10:45AM EST
Recent Progress on the Theory of the 2DES at larger rs
Theoretical and experimental studies of two-dimensional electron systems (2DES) have played a pivotal role in the history of quantum condensed matter physics. It is also an old, and long-studied problem, about which much is well known. In this talk, I will describe some significant new results obtained by some brilliant collaborators of mine concerning the quantum phases of the 2DES at large and intermediate values of rs, where rs is the Wigner-Seitz radius of the 2DES in units of the effective Bohr radius. (Large rs corresponds to low enteron density.). These include two new results for the simple 2DES: 1) A more complete analysis of tunneling processes deep in the Wigner crystal (WC) phase (large rs), which in particular provides suggestive evidence of a self-doping instability. 2) A variational Monte Carlo (VMC) study of the phase diagram in the presence of screening gates, yielding a quantitative estimate of the critical gate-distance necessary for the existence of a WC. We also explore several new aspects of multi-component 2DES (i.e. that arises in a multi-valley semiconductor): 1) An asymptotic large rs examination of valley ordering in the WC phase. 2) Combined VMC and approximate analytic studies of generalized ferromagnetism in the fluid phases at intermediate rs, including the observation of a spin unpolarized electron-nematic phase in a two-valley 2DES of the sort that occurs in AlAs heterostructures.
K-S. Kim, I. Esterlis, C. Murthy, and SAK, “Dynamical defects in a two-dimensional Wigner crystal: self-doping and kinetic magnetism,” Phys. Rev. B 109, 235130 (2024).
V. Calvera, SAK, and E. Berg, “Pseudo-spin order of Wigner crystals in multi-valley electron gases,” Fiz. Nyzk. Temp. 49, 747-769 (2023).
K-S. Kim, C. Murthy, A. Pandey, and SAK, “Interstitial-induced ferromagnetism in a two-dimensional Wigner crystal,” Phys. Rev. Lett. 129, 227202 (2022).
A. Valenti, V. Calvera, SAK, E. Berg, and S. D.Huber, “Nematic metal in a multi-valley electron gas: Variational Monet Carlo analysis and application to AlAs,” Phys. Rev. Lett. 132, 266501 (2024).
V. Calvera, E. Berg, and SAK, “Symmetry-determined generalized ferromagnetism in multi-valley electron fluids,” arXiv:2507.05344 (2025).
A. Valenti, V. Calvera, Y. Yang, M.A. Morales, SAK, I. Esterlis, and S. Zhang, “Critical gate distance for Wigner crystallization in the two-dimensional electron gas,” arXiv:2501.16430 (2025).
V. Calvera, A. Valenti, S.D. Huber, E. Berg, and SAK, “Theory of Coulomb driven nematicity in a multi-valley two-dimensional electron gas,” PRB 111, 155135 (2025).