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arXiv · 2202.05029

Moments and multiplets in moir\'e materials: A pseudo-fermion functional renormalization group for spin-valley models

Lasse Gresista·Dominik Kiese·Simon Trebst
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Abstract

The observation of strongly-correlated states in moir\'e systems has renewed the conceptual interest in magnetic systems with higher SU(4) spin symmetry, e.g. to describe Mott insulators where the local moments are coupled spin-valley degrees of freedom. Here, we discuss a numerical renormalization group scheme to explore the formation of spin-valley ordered and unconventional spin-valley liquid states at zero temperature based on a pseudo-fermion representation. Our generalization of the conventional pseudo-fermion functional renormalization group approach for $\mathfrak{su}$(2) spins is capable of treating diagonal and off-diagonal couplings of generic spin-valley exchange Hamiltonians in the self-conjugate representation of the $\mathfrak{su}$(4) algebra. To achieve proper numerical efficiency, we derive a number of symmetry constraints on the flow equations that significantly limit the number of ordinary differential equations to be solved. As an example system, we investigate a diagonal SU(2)$_{\textrm{spin}}$ $\otimes$ U(1)$_{\textrm{valley}}$ model on the triangular lattice which exhibits a rich phase diagram of spin and valley ordered phases.

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Lasse Gresista, Dominik Kiese, Simon Trebst. 2022-02-10. Moments and multiplets in moir\'e materials: A pseudo-fermion functional renormalization group for spin-valley models. https://doi.org/10.1140/epjb/s10051-022-00373-2

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