Collective bulk carrier delocalization driven by electrostatic surface charge accumulation

Abstract

In the classic transistor, the number of electric charge carriers--and thus the electrical conductivity--is precisely controlled by external voltage, providing electrical switching capability. This simple but powerful feature is essential for information processing technology, and also provides a platform for fundamental physics research. As the number of charges essentially determines the electronic phase of a condensed-matter system, transistor operation enables reversible and isothermal changes in the system's state, as successfully demonstrated in electric-field-induced ferromagnetism and superconductivity. However, this effect of the electric field is limited to a channel thickness of nanometres or less, owing to the presence of Thomas-Fermi screening. Here we show that this conventional picture does not apply to a class of materials characterized by inherent collective interactions between electrons and the crystal lattice. We prepared metal-insulator-semiconductor field-effect transistors based on vanadium dioxide--a strongly correlated material with a thermally driven, first-order metal-insulator transition well above room temperature--and found that electrostatic charging at a surface drives all the previously localized charge carriers in the bulk material into motion, leading to the emergence of a three-dimensional metallic ground state. This non-local switching of the electronic state is achieved by applying a voltage of only about one volt. In a voltage-sweep measurement, the first-order nature of the metal-insulator transition provides a non-volatile memory effect, which is operable at room temperature. Our results demonstrate a conceptually new field-effect device, extending the concept of electric-field control to macroscopic phase control.

Emergent functions of quantum materials

“…Figure 2b exemplifies the electricdouble-layer transistor (EDLT) gate control of the MIT in VO 2 films 18 ; a clear MIT is observed upon gating, ascribed to the fillingcontrol Mott transition, although its doping mechanism is still controversial 18,19 . As shown in the upper panel of Fig.…”

Hydrogen Diffusion and Stabilization in Single-Crystal VO2 Micro/Nanobeams by Direct Atomic Hydrogenation

“…[5][6][7][8] In addition, this material has attracted much attention for its potential applications in ultrafast optical and electrical switching. [9][10][11][12][13] Therefore, much effort has been made to modulate the MIT by various approaches such as strain engineering, 14,15 ionic liquid gating, [16][17][18] electric field-induced oxygen vacancy, 19 and chemical doping. [20][21][22][23][24][25] In terms of chemical doping, using metal elements such as tungsten during growth can dramatically change the transition properties 20,26 , but it is an irreversible process.…”

Electric-Field-Induced Superconductivity on an Organic/Oxide Interface

“…41,42) Electricfield-induced superconductivity was also reported on layered superconductor compounds. 43,44) Electric field-effect switching of ferromagnetism and a charge ordered state was reported on ferromagnetic semiconductors, ferromagnetic thin film metals and oxide thin films, [45][46][47] which suggests that electric field-effect doping will be a standard method to examine the physical properties of a material, similar to high-pressure experiments and high magnetic field experiments. …”