Kavli Affiliate: Jing Wang
| First 5 Authors: Kejie Bao, Kejie Bao, , ,
| Summary:
Experimental studies on moir’e materials have predominantly focused on
twisted hexagonal lattice with low-energy states near the $Gamma$- or
K-points, where the electronic dispersion is typically isotropic. In contrast,
we introduce a class of semiconducting transition metal carbides (MXenes)
$M_2$C$T_2$ ($M$ = Ti, Zr, Hf, Sc, Y; $T$ = O, F, Cl) as a new platform for
M-valley moir’e materials, which exhibit pronounced anisotropic properties.
Using Ti$_2$CO$_2$ and Zr$_2$CO$_2$ as representative examples, we perform
large-scale emphab initio calculations and demonstrate that their AB-stacked
twisted homobilayer hosts three threefold rotational-symmetry-related M-valleys
with time-reversal symmetry. These systems show striking anisotropic band
flattening in the conduction band minimum. To elucidate the underlying physics,
we construct a simplified moir’e Hamiltonian that captures the essential
features of the band structure, revealing the origins of anisotropic flattening
through the mechanisms of band folding and interlayer tunneling. Our findings
expand the current landscape of moir’e materials, establishing valley- and
spin-degenerate, two-dimensional arrays of quasi-one-dimensional systems as
promising platforms for exploring many interesting correlated electronic
phases.
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