Observation of spontaneous valley polarization of itinerant electrons

Abstract

Memory or transistor devices based on electron's spin rather than its charge degree of freedom offer certain distinct advantages and comprise a cornerstone of spintronics. Recent years have witnessed the emergence of a new field, valleytronics, which seeks to exploit electron's valley index rather than its spin. An important component in this quest would be the ability to control the valley index in a convenient fashion. Here we show that the valley polarization can be switched from zero to one by a small reduction in density, simply tuned by a gate bias, in a two-dimensional electron system. This phenomenon arises fundamentally as a result of electron-electron interaction in an itinerant, dilute electron system. Essentially, the kinetic energy favors an equal distribution of electrons over the available valleys, whereas the interaction between electrons prefers single-valley occupancy below a critical density. The gate-bias-tuned transition we observe is accompanied by a sudden, two-fold change in sample resistance, making the phenomenon of interest for potential valleytronic transistor device applications. Our observation constitutes a quintessential demonstration of valleytronics in a very simple experiment.

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Cited by in corpus (19)

• Anisotropic, two-dimensional, disordered Wigner solid
• Ground state phases of the two-dimension electron gas with a unified variational approach
• Interstitial-induced ferromagnetism in a two-dimensional Wigner crystal
• Robust Quantum Hall Ferromagnetism near a Gate-Tuned ν = 1 Landau Level Crossing
• Nematic metal in a multi-valley electron gas: Variational Monte Carlo analysis and application to AlAs
• Tuning multiple Landau Quantization in Transition-Metal Dichalcogenide with Strain
• Pseudo-spin order of Wigner crystals in multi-valley electron gases
• Local noise spectroscopy of Wigner crystals in two-dimensional materials
• Theory of Coulomb driven nematicity in a multi-valley two-dimensional electron gas
• Discovery of an insulating ferromagnetic phase of electrons in two dimensions
• Fractional quantum Hall valley ferromagnetism in the extreme quantum limit
• Supercell Wannier functions and a faithful low-energy model for Bernal bilayer graphene
• Ferromagnetic semimetal and charge-density wave phases of interacting electrons in a honeycomb moiré potential
• Valley polarization transition in a two-dimensional electron gas
• Spin susceptibility in interacting two-dimensional semiconductors and bilayer systems at first order: Kohn anomalies and spin density wave ordering
• Critical gate distance for Wigner crystallization in the two-dimensional electron gas
• Apparent inconsistency between Streda formula and Hall conductivity in reentrant integer quantum anomalous Hall effect in twisted MoTe${}_2$
• Developing fractional quantum Hall states at $\nu$ = $\frac{1}{7}$ and $\frac{2}{11}$ in the presence of significant Landau level mixing
• An unusual first order phase transition in a 2D superconductor