English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In this paper we explore possible phases arising from doping neutral excitonsinto a Mott insulator in the context of moir\'e bilayers. We consider twomoir\'e layers coupled together only through inter-layer repulsion and there isa U(2)$\times$ U(2) symmetry. The densities of the two layers can be tuned tobe $n_t=x,n_b=1-x$ with $n_t+n_b=1$. $x=0$ limit is a layer polarized Mottinsulator and small $x$ regime can be reached by doping inter-layer excitons atdensity $x$. Charge gap can remain finite at small $x$, as is demonstratedexperimentally in the WSe$_2$-hBN-WSe$_2$/WS$_2$ system. To capture theintertwinement of the spin and exciton degree of freedom, we propose afour-flavor spin model. In addition to the obvious possibility of singleexciton condensation phase, we also identified more exotic physics withfractionalization: (I) We define spin gap $\Delta_t, \Delta_b$ for the twolayers respectively. As long as the spin gap at either layer is finite, singleexciton condensation is impossible and we can only have paired excitoncondensation. If both spin gaps are finite, it can be a fractional excitonsuperfluid with paired exciton condensation coexisting with $Z_2$ spin liquid.Numerical evidences for such a phase will be provided. (II) If the layerpolarized Mott insulator at $x=0$ is in a U(1) spin liquid with spinon Fermisurface, the natural phase at $x>0$ hosts neutral Fermi surface formed byfermionic excitons. There are metallic counter-flow transport and also Friedeloscillations in layer polarization in this exotic phase. Our numericalsimulation in one dimension observes an analog of this neutral Fermi surfacephase. (III) There could be a metal-insulator transition (MIT) by tuning $x$ inthe universality class of a bandwidth tuned MIT. We provide one theory for sucha continuous Mott transition and predicted a universal drag resistivity.

Doping a Mott insulator with excitons in moir\'e bilayer: fractional superfluid, neutral Fermi surface and Mott transition