Abstract
We report anomalous resistance leaps and drops in VO2 nanowires with operating current density and direction, showing reversible and nonvolatile switching. This event is associated with the metal–insulator phase transition (MIT) of local nanodomains with coexistence states of metallic and insulating phases induced by thermoelectric cooling and heating effects. Because the interface of metal and insulator domains has much different Peltier coefficient, it is possible that a significant Peltier effect would be a source of the local MIT. This operation can be realized by one-dimensional domain configuration in VO2 nanowires because one straight current path through the electronic domain-interface enables theoretical control of thermoelectric effects. This result will open a new method of reversible control of electronic states in correlated electron materials.
Highlights
The emergence of mixed electronic phases is a characteristic in correlated electron materials.[1,2,3] The coexistence states naturally form a nontraditional interface consisting of different types of electronic phases, such as metallic and insulating states, which is entirely different from a conventional rigid heterojunction composed of two different materials
This event is associated with the metal–insulator phase transition (MIT) of local nanodomains with coexistence states of metallic and insulating phases induced by thermoelectric cooling and heating effects
Discrete resistance increases are observable in VO2 nanowires under a current bias on the order of 108 A/m2, while they are not seen in the thin films
Summary
The emergence of mixed electronic phases is a characteristic in correlated electron materials.[1,2,3] The coexistence states naturally form a nontraditional interface consisting of different types of electronic phases, such as metallic and insulating states, which is entirely different from a conventional rigid heterojunction composed of two different materials. Our scenario for the reversible control of resistivity is to exert cooling and heating action, encouraging the MIT by the current across the interface between metal and insulating domains that have different Seebeck coefficients. The Seebeck coefficient of insulating (∼400 μV/K) and metallic states (∼20 μV/K) in VO2 is widely different.[21,22] To realize the expected control, one-dimensional (1D) alignment of metal–insulator domains is indispensable, and nanowires can allow effective and theoretical thermoelectric cooling and heating because there is only one straight current path through the interface. If a local temperature change induced by thermoelectric cooling and heating effects crosses the MIT transition points in a domain, the first-order transition through an electronic avalanche within a domain would be realized, as seen in the right figure of Fig. 1(a). We waited 10 ms after applying a current bias at each point, which enables a stable state for local temperature because the MIT response induced by thermoelectric effects is very quick and reaches a stable state on the order of microseconds.[23]
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