Appearance of “Fragile” Fermi Liquids in Finite-Width Mott Insulators Sandwiched between Metallic Leads

Using inhomogeneous dynamical mean-field theory, we show that the normal-metal proximity effect could force any finite number of Mott-insulating “barrier” planes sandwiched between semi-infinite metallic leads to become “fragile” Fermi liquids. They are fully Fermi-liquid-like at $T=0$, leading to a restoration of lattice periodicity at zero frequency, with a well-defined Fermi surface, and perfect (ballistic) conductivity. However, the Fermi-liquid character can rapidly disappear at finite $\omega$, $V$, $T$, disorder, or magnetism, all of which restore the expected quantum tunneling regime, leading to fascinating possibilities for nonlinear response in devices.

Figure 1

Local spectral function at the barrier plane for a single-barrier-plane multilayer, for $T=0.01$, and a range of $U$’s (increasing from top to bottom near zero frequency).

Figure 2

Local spectral function of the five-barrier-plane multilayer for $U=16$, and three different temperatures: (a) $T=0.01$, (b) $T=0.001$, and (c) $T=0.0001$. We show the three inequivalent barrier planes ($N=1$ is next to the interface, $N=3$ is at the center). The insets show blowups of the low frequency region.