Mott qubit and fractron in a Mott system

There is an instability for the Mott IMT(Insulator-to-Metal Transition) not accompanied with the structural phase transition, excitation (U at metal from U_c at insulator) of the Mott criterion n_c from a doped Mott insulator; such as the instability at an effective mass of carrier, m*/m=1/[1-(U/U_c)²], in the Brinkman-Rice picture, where U is the on-site Coulomb energy between electrons and U_c is the critical Coulomb energy[1,2]. Due to the instability, near U/U_c=1, two phases of Mott insulator l0> and metal l1> are observed in a measurement region. They can be linearly combined like a superposition of Ψ=αl0>+βl1> and can also be entangled (coupled) as Ψ₁Ψ₂. In a Mott system, the metallic carrier charge is an fractional effective charge (fractron) coming from average of the measurement region. As an example, in VO₂, the IMT oscillation as evidence of the fractron was observed[3] and the coupling was also measured[4]. Thus, we suggest a Mott qubit. [1]PRB 2(1970)4302. [2]Physica C 341-348(2000)259. [3]J.Appl.Phys.107(2010)023702. [4]Sci. Report.4(2014)4964.