Collaborative Research: Search for the Zero-Magnetic-Field Wigner Solid

Northeastern University, Boston MA

Investigators

Abstract

****TECHNICAL ABSTRACT**** First predicted by Eugene Wigner in 1934, the realization of the electronic solid (Wigner Crystal) which forms when the interactions between electrons strongly exceed their kinetic energy has been a long-standing challenge. A classical Wigner crystal has been realized for electrons on the surface of liquid helium, and possible evidence of crystallization of quantum electron systems has been obtained in strong magnetic field. The aim of this project is to realize the quantum Wigner crystal in zero field, to obtain definitive evidence of its existence, and to study its formation as a function of temperature, magnetic field, electron density and disorder. The search for the zero-field Wigner solid is especially promising at this time because: (a) we have recently obtained compelling evidence that there is a genuine phase transition in a dilute 2D electron system driven by interactions to a low-density phase that may be a precursor phase or the Wigner Crystal itself; (b) samples are now available that far exceed the quality of the samples used 20 years ago in which measurements suggested the possibility of Wigner crystallization. We will investigate the nonlinear transport and noise spectra of low-density, low-disorder, strongly correlated two-dimensional electron systems in metal-oxide semiconductor field-effect transistors (MOSFETs) and strained silicon quantum wells in Si/SiGe heterostructures. This project will support the education of a PhD student in these advanced technologies, which has historically shown itself to be excellent training for many scientific careers from academia to our most advanced technology industries. ****NON-TECHNICAL ABSTRACT**** In most metals, electrons behave like a gas and move randomly through the structure formed by the massive positive ions. Eugene Wigner predicted in 1934 that when the energy of motion of the electrons is much lower than the energy of interaction between them, the electron gas will instead freeze into a lattice, forming a "Wigner crystal" or "Wigner glass". Realized for electrons on the surface of liquid helium, and possibly in semiconductors in strong magnetic field, the Wigner solid has not been found in semiconductors in the absence of magnetic field. By measurements of the nonlinear resistance and noise spectra of low-density two-dimensional electron systems in silicon metal-oxide semiconductor field-effect transistors (MOSFETs) and Si/Si-Ge heterostructures, we plan to realize and investigate the long sought-after zero field Wigner crystal, thereby providing opportunities for studies in a heretofore unexplored region, and adding a deeper fundamental understanding of semiconductors - materials that are of great importance to our current technology. This project will support the education of a PhD student in these advanced technologies, which has historically shown itself to be excellent training for many scientific careers from academia to our most advanced technology industries.