skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: From deconfined spinons to coherent magnons in an antiferromagnetic Heisenberg chain with long range interactions
We study the nature of the excitations of an antiferromagnetic (AFM) Heisenberg chain with staggered long range interactions using the time-dependent density matrix renormalization group method and by means of a multi-spinon approximation. The chain undergoes true symmetry breaking and develops long range order, transitioning from a gapless spin liquid to a gapless ordered AFM phase. The spin dynamic structure factor shows that the emergence of Néel order can be associated to the formation of bound states of spinons that become coherent magnons. The quasiparticle band leaks out from the two-spinon continuum that is pushed up to higher energies. Our physical picture is also supported by an analysis of the behavior of the excitations in real-time.  more » « less
Award ID(s):
1807814
PAR ID:
10303817
Author(s) / Creator(s):
 ;  
Date Published:
Journal Name:
SciPost Physics
Volume:
10
Issue:
5
ISSN:
2542-4653
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Nature Communications)
    Abstract The combination of a geometrically frustrated lattice, and similar energy scales between degrees of freedom endows two-dimensional Kagome metals with a rich array of quantum phases and renders them ideal for studying strong electron correlations and band topology. The Kagome metal, FeGe is a noted example of this, exhibiting A-type collinear antiferromagnetic (AFM) order atTN ≈ 400 K, then establishes a charge density wave (CDW) phase coupled with AFM ordered moment belowTCDW ≈ 110 K, and finally forms ac-axis double cone AFM structure aroundTCanting ≈ 60 K. Here we use neutron scattering to demonstrate the presence of gapless incommensurate spin excitations associated with the double cone AFM structure of FeGe at temperatures well aboveTCantingandTCDWthat merge into gapped commensurate spin waves from the A-type AFM order. Commensurate spin waves follow the Bose factor and fit the Heisenberg Hamiltonian, while the incommensurate spin excitations, emerging belowTNwhere AFM order is commensurate, start to deviate from the Bose factor aroundTCDW, and peaks atTCanting. This is consistent with a critical scattering of a second order magnetic phase transition with decreasing temperature. By comparing these results with density functional theory calculations, we conclude that the incommensurate magnetic structure arises from the nested Fermi surfaces of itinerant electrons and the formation of a spin density wave order. 
    more » « less
  2. ; ; (, SciPost Physics)
    We study a generalized quantum spin ladder with staggered long rangeinteractions that decay as a power-law with exponent \alpha α .Using large scale quantum Monte Carlo (QMC) and density matrixrenormalization group (DMRG) simulations, we show that this modelundergoes a transition from a rung-dimer phase characterized by anon-local string order parameter, to a symmetry broken N'eel phase. Wefind evidence that the transition is second order. In the magneticallyordered phase, the spectrum exhibits gapless modes, while excitations inthe gapped phase are well described in terms of triplons – bound statesof spinons across the legs. We obtain the momentum resolved spin dynamicstructure factor numerically and find a well defined triplon band thatevolves into a gapless magnon dispersion across the transition. Wefurther discuss the possibility of deconfined criticality in thismodel. 
    more » « less
  3. ; (, Journal of High Energy Physics)
    A<sc>bstract</sc> We analyze a Higgs transition from a U(1) Dirac spin liquid to a gapless ℤ2spin liquid. This ℤ2spin liquid is of relevance to the spinS= 1/2 square lattice antiferromagnet, where recent numerical studies have given evidence for such a phase existing in the regime of high frustration between nearest neighbor and next-nearest neighbor antiferromagnetic interactions (theJ1-J2model), appearing in a parameter regime between the vanishing of Néel order and the onset of valence bond solid ordering. The proximate Dirac spin liquid is unstable to monopole proliferation on the square lattice, ultimately leading to Néel or valence bond solid ordering. As such, we conjecture that this Higgs transition describes the critical theory separating the gapless ℤ2spin liquid of theJ1-J2model from one of the two proximate ordered phases. The transition into the other ordered phase can be described in a unified manner via a transition into an unstable SU(2) spin liquid, which we have analyzed in prior work. By studying the deconfined critical theory separating the U(1) Dirac spin liquid from the gapless ℤ2spin liquid in a 1/Nfexpansion, withNfproportional to the number of fermions, we find a stable fixed point with an anisotropic spinon dispersion and a dynamical critical exponentz≠ 1. We analyze the consequences of this anisotropic dispersion by calculating the angular profiles of the equal-time Néel and valence bond solid correlation functions, and we find them to be distinct. We also note the influence of the anisotropy on the scaling dimension of monopoles. 
    more » « less
  4. ; ; ; ; ; ; (, Advanced Functional Materials)
    Abstract Spin excitations, including magnons and spinons, can carry thermal energy and spin information. Studying spin‐mediated thermal transport is crucial for spin caloritronics, enabling efficient heat dissipation in microelectronics and advanced thermoelectric applications. However, designing quantum materials with controllable spin transport is challenging. Here, highly textured spin‐chain compound Ca2CuO3is synthesized using a solvent‐cast cold pressing technique, aligning 2D nanostructures with spin chains perpendicular to the pressing direction. The sample exhibits high thermal conductivity anisotropy and an excellent room‐temperature thermal conductivity of 12 ± 0.7 W m−1K−1, surpassing all polycrystalline quantum magnets. Such a high value is attributed to the significant spin‐mediated thermal conductivity of 10 ± 1 W m−1K−1, the highest reported among all polycrystalline quantum materials. Analysis through a 1D kinetic model suggests that near room‐temperature, spinon thermal transport is dominated by coupling with high‐frequency phonons, while extrinsic spinon‐defect scattering is negligible. Additionally, this method is used to prepare textured La2CuO4, exhibiting highly anisotropic magnon thermal transport and demonstrating its broad applicability. A distinct role of defect scattering in spin‐mediated thermal transport is observed in two spin systems. These findings open new avenues for designing quantum materials with controlled spin transport for thermal management and energy conversion. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; (, arXivorg)
    Electronic spins can form long-range entangled phases of condensed matter named quantum spin liquids. Their existence is conceptualized in models of two- or three-dimensional frustrated magnets that evade symmetry-breaking order down to zero temperature. Quantum spin ice (QSI) is a theoretically well-established example described by an emergent quantum electrodynamics, with excitations behaving like photon and matter quasiparticles. The latter are fractionally charged and equivalent to the `spinons' emerging from coherent phases of singlets in one dimension, where clear experimental proofs of fractionalization exist. However, in frustrated magnets it remains difficult to establish consensual evidence for quantum spin liquid ground states and their fractional excitations. Here, we use backscattering neutron spectroscopy to achieve extremely high resolution of the time-dependent magnetic response of the candidate QSI material Ce2Sn2O7. We find a gapped spectrum featuring a threshold and peaks that match theories for pair production and propagation of fractional matter excitations (spinons) strongly coupled to a background gauge field. The observed peaks provide evidence for a QSI through spectroscopic signatures of space-time symmetry fractionalization, while the threshold behavior corroborates the regime of strong light-matter interaction predicted for the emergent universe in a QSI. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email