Electric field effect near the metal-insulator transition of a two-dimensional electron system in SrTiO3

Abstract

SmTiO3/SrTiO3 interfaces exhibit a two-dimensional electron system with carrier densities in the order of 3 × 1014 cm−2 due to the polar discontinuity at the interface. Here, electric field effect is used to investigate an electron system at this interface whose carrier density has been depleted substantially by the gate metal and by reducing the thickness of the SmTiO3. At zero applied gate voltage, the sheet resistance exceeds the quantum resistance, h/e2, by more than an order of magnitude, and the SrTiO3 channel is in the hopping transport regime. The electric field modulates the carrier density in the channel, which approaches the transition to a metal at positive gate bias. The channel resistances are found to scale by a single parameter that depends on the gate voltage, similar to two-dimensional electron systems in high-quality semiconductors.

Two-dimensional electron gas in a metal/amorphous oxide interface with spin-orbit interaction

“…20 For perovskites systems this metal-insulator transition has been studied as a function of temperature and by modulating carrier densities by means of gating. 39,40 Here, the carrier density and the Rashba effect-inducing interfacial electric field are provided by the dielectric characteristics of the underlying Cu supporting film. The parameters, such as dc conductivities σ 0 xx , σ 0 zz , and mean times of life τ xx and τ zz of the free electron contribution to the 2DEG are presented in Table I as functions of underlying Cu film thickness.…”

Novel Metal-Insulator Transition at the SmTiO3/SrTiO3 Interface

“…4). The room temperature n s values systematically scale with the SmTiO 3 thickness [14]. They are 1.4 × 10 14 , 2 × 10 14 , 2.1 × 10 14 , and 2.7 × 10 14 cm −2 for the samples with 60 nm SrTiO 3 and 3, 5, 7, and 20 u.c.…”

“…This insulating state preempts correlation-induced MITs or other phenomena that may emerge out of an itinerant correlated electron system. MITs near the Mott-Ioffe-Regel limit have been observed in electron systems at LaAlO 3 =SrTiO 3 [13] and SmTiO 3 =SrTiO 3 interfaces [14].…”

“…When SmTiO 3 layers are reduced to a few unit cells (u.c. ), the sheet carrier densities are reduced below this value and depend systematically on the SmTiO 3 thickness [14]. Given carrier densities that are not close to either one of the two limiting cases discussed above, conventional wisdom would suggest that a correlationdriven MIT is unlikely to occur.…”

Non-Fermi-liquid behavior and doping asymmetry in an organic Mott insulator interface

“…At 20-50 K, this sample exhibits an IMC at gate voltage V G =0.34 V, namely the sign of dρ s /dT changes by the gate voltage. The resistivity at 0.34 V is close to h/e 2 , which corresponds to ρ MIR for two-dimensional metal with an isotropic Fermi surface [16,17]. By further electron doping, the temperature dependence of ρ s approaches that of a Fermi liquid at low temperatures.…”