We study symmetry-broken phases in twisted bilayer graphene at small filling above charge neutrality and at van Hove filling. We argue that the Landau functionals for the particle-hole order parameters at these fillings both have an approximate SU(4) symmetry, but differ in the sign of quartic terms. We determine the order parameter manifold of the ground state and analyze its excitations. For small fillings, we find a strong first-order transition to an SU(3)⊗U(1) manifold of orders that break spin-valley symmetry and induce a 3-1 splitting of fermionic excitations. For van Hove filling, we find a weak first-order transition to an SU(2)⊗SU(2)⊗U(1) manifold of orders that preserves the twofold band degeneracy. We discuss the effect of particle-hole orders on superconductivity and compare with strong-coupling approaches.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1103/PhysRevLett.128.227601 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
SU() symmetry of coherent photons controlled by rotated waveplates.
Heliyon
July 2024
Center for Exploratory Research Laboratory, Research & Development Group, Hitachi, Ltd., 1-280 Higashi-Koigakubo, Kokubunji, 185-8601, Tokyo, Japan.
The coherent state from a laser source has spin and orbital degrees of freedom, which allow an arbitrary superposition state among orthogonal states with varying amplitudes and phases. Here, we theoretically show coherent photons with SU() symmetry are characterised by expectation values of angular momentum shown on a hypersphere in SO( ) space. To demonstrate expected unitary transformations in experiments, we have constructed generators of transformations in the Lie group simply by combining widely available optical components such as waveplates and vortex lenses.
View Article and Find Full Text PDFUnveiling a critical stripy state in the triangular-lattice SU(4) spin-orbital model.
Sci Bull (Beijing)
May 2022
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; Songshan Lake Materials Laboratory, Dongguan, Dongguan 523808, China; Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China; CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China. Electronic address:
The simplest spin-orbital model can host a nematic spin-orbital liquid state on the triangular lattice. We provide clear evidence that the ground state of the SU(4) Kugel-Khomskii model on the triangular lattice can be well described by a "single" Gutzwiller projected wave function with an emergent parton Fermi surface, despite it exhibits strong finite-size effect in quasi-one-dimensional cylinders. The finite-size effect can be resolved by the fact that the parton Fermi surface consists of open orbits in the reciprocal space.
View Article and Find Full Text PDFSpin-orbit microlaser emitting in a four-dimensional Hilbert space.
Nature
December 2022
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
A step towards the next generation of high-capacity, noise-resilient communication and computing technologies is a substantial increase in the dimensionality of information space and the synthesis of superposition states on an N-dimensional (N > 2) Hilbert space featuring exotic group symmetries. Despite the rapid development of photonic devices and systems, on-chip information technologies are mostly limited to two-level systems owing to the lack of sufficient reconfigurability to satisfy the stringent requirement for 2(N - 1) degrees of freedom, intrinsically associated with the increase of synthetic dimensionalities. Even with extensive efforts dedicated to recently emerged vector lasers and microcavities for the expansion of dimensionalities, it still remains a challenge to actively tune the diversified, high-dimensional superposition states of light on demand.
View Article and Find Full Text PDFPerturbative Quantum Monte Carlo Method for Nuclear Physics.
Phys Rev Lett
June 2022
Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn, Germany.
While first order perturbation theory is routinely used in quantum Monte Carlo (QMC) calculations, higher-order terms present significant numerical challenges. We present a new approach for computing perturbative corrections in projection QMC calculations. We demonstrate the method by computing nuclear ground state energies up to second order for a realistic chiral interaction.
View Article and Find Full Text PDFSU(4) Symmetry in Twisted Bilayer Graphene: An Itinerant Perspective.
Phys Rev Lett
June 2022
School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
We study symmetry-broken phases in twisted bilayer graphene at small filling above charge neutrality and at van Hove filling. We argue that the Landau functionals for the particle-hole order parameters at these fillings both have an approximate SU(4) symmetry, but differ in the sign of quartic terms. We determine the order parameter manifold of the ground state and analyze its excitations.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!