59 research outputs found
Foliated fracton order in the Majorana checkerboard model
We establish the presence of foliated fracton order in the Majorana
checkerboard model. In particular, we describe an entanglement renormalization
group transformation which utilizes toric code layers as resources of
entanglement, and furthermore discuss entanglement signatures and fractional
excitations of the model. In fact, we give an exact local unitary equivalence
between the Majorana checkerboard model and the semionic X-cube model augmented
with decoupled fermionic modes. This mapping demonstrates that the model lies
within the X-cube foliated fracton phase.Comment: 13 pages, 17 figure
Electrical control of spin and valley in spin-orbit coupled graphene multilayers
Electrical control of magnetism has been a major techonogical pursuit of the
spintronics community, owing to its far-reaching implications for data storage
and transmission. Here, we propose and analyze a new mechanism for electrical
switching of isospin, using chiral-stacked graphene multilayers, such as bernal
bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition
metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced
spin-orbit coupling from the TMD, we demonstrate electrical switching of
correlation-induced spin and/or valley polarization, by reversing a
perpendicular displacement field or the chemical potential. We substantiate our
proposal with both analytical arguments and self-consistent Hartree-Fock
numerics. Finally, we illustrate how the relative alignment of the TMDs,
together with the top and bottom gate voltages, can be used to selectively
switch distinct isospin flavors, putting forward correlated van der Waals
heterostructures as a promising platform for spintronics and valleytronics.Comment: 5 pages, 4 figures. (v2) Significant re-write correcting the magnetic
moment, SM adde
Inter-valley coherent order and isospin fluctuation mediated superconductivity in rhombohedral trilayer graphene
Superconductivity was recently discovered in rhombohedral trilayer graphene
(RTG) in the absence of a moir\'e potential. Superconductivity is observed
proximate to a metallic state with reduced isospin symmetry, but it remains
unknown whether this is a coincidence or a key ingredient for
superconductivity. Using a Hartree-Fock analysis and constraints from
experiments, we argue that the symmetry breaking is inter-valley coherent (IVC)
in nature. We evaluate IVC fluctuations as a possible pairing glue, and find
that they lead to chiral unconventional superconductivity when the fluctuations
are strong. We further elucidate how the inter-valley Hund's coupling
determines the spin-structure of the IVC ground state and breaks the degeneracy
between spin-singlet and triplet superconductivity. Remarkably, if the normal
state is spin-unpolarized, we find that a ferromagnetic Hund's coupling favors
spin-singlet superconductivity, in agreement with experiments. Instead, if the
normal state is spin-polarized, then IVC fluctuations lead to spin-triplet
pairing.Comment: 8 + 22 pages, 3 + 5 figures; (v2) 8 + 24 pages, 3 + 6 figures,
additional discussion of pairing symmetries; (v3) 9 + 25 pages, 3 + 7
figures, added phase diagram and correlation length estimat
Fermionic Isometric Tensor Network States in Two Dimensions
We generalize isometric tensor network states to fermionic systems, paving
the way for efficient adaptations of 1D tensor network algorithms to 2D
fermionic systems. As the first application of this formalism, we developed and
benchmarked a time-evolution block-decimation (TEBD) algorithm for real-time
and imaginary-time evolution. The imaginary-time evolution produces
ground-state energies for gapped systems, systems with a Dirac point, and
systems with gapless edge mode to good accuracy. The real-time TEBD captures
the chiral edge dynamics on the boundary of a Chern insulator.Comment: 5 + 5 pages, 5 + 4 figure
Topological magnets and magnons in twisted bilayer MoTe and WSe
Twisted homobilayer transition metal dichalcogenide (TMD) offers a versatile
platform for exploring band topology, interaction-driven phases, and magnetic
orders. We study the interaction-driven phases in twisted TMD homobilayers and
their low-energy collective excitations, focusing on the effect of band
topology on magnetism and its thermal stability. From Hartree-Fock theory of
the continuum model, we identify several magnetic and topological phases. By
tuning the displacement field, we find two phase transitions involving a change
in topology and magnetism respectively. We analyze the magnon spectrum,
revealing the crucial role of band topology in stabilizing 2D ferromagnetism by
amplifying easy-axis magnetic anisotropy, resulting in a large magnon gap of up
to 7 meV. As the magnon gap is directly tied to the stability of the magnetic
phase to thermal fluctuations, our findings have several important experimental
implications.Comment: 5 pages, 4 figures. (v2) Added S
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