scholarly journals Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Sala ◽  
M. B. Stone ◽  
Binod K. Rai ◽  
A. F. May ◽  
Pontus Laurell ◽  
...  
Keyword(s):  
Disordered Systems ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Wave Theory ◽  
Inelastic Neutron ◽  
Quantum Spin ◽  
Honeycomb Lattice ◽  
Quantum Magnetism ◽  
Van Hove Singularity ◽  
Sharp Feature

AbstractIn quantum magnets, magnetic moments fluctuate heavily and are strongly entangled with each other, a fundamental distinction from classical magnetism. Here, with inelastic neutron scattering measurements, we probe the spin correlations of the honeycomb lattice quantum magnet YbCl3. A linear spin wave theory with a single Heisenberg interaction on the honeycomb lattice, including both transverse and longitudinal channels of the neutron response, reproduces all of the key features in the spectrum. In particular, we identify a Van Hove singularity, a clearly observable sharp feature within a continuum response. The demonstration of such a Van Hove singularity in a two-magnon continuum is important as a confirmation of broadly held notions of continua in quantum magnetism and additionally because analogous features in two-spinon continua could be used to distinguish quantum spin liquids from merely disordered systems. These results establish YbCl3 as a benchmark material for quantum magnetism on the honeycomb lattice.

scholarly journals Field-induced quantum spin disordered state in spin-1/2 honeycomb magnet Na2Co2TeO6

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaoting Lin ◽  
Jaehong Jeong ◽  
Chaebin Kim ◽  
Yao Wang ◽  
Qing Huang ◽  
...  
Keyword(s):  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Quantum Spin ◽  
Honeycomb Lattice ◽  
Quantum Magnetism ◽  
Spin Liquids ◽  
Field Range ◽  
Spin Orbital ◽  
Effective Spin

AbstractSpin-orbit coupled honeycomb magnets with the Kitaev interaction have received a lot of attention due to their potential of hosting exotic quantum states including quantum spin liquids. Thus far, the most studied Kitaev systems are 4d/5d-based honeycomb magnets. Recent theoretical studies predicted that 3d-based honeycomb magnets, including Na2Co2TeO6 (NCTO), could also be a potential Kitaev system. Here, we have used a combination of heat capacity, magnetization, electron spin resonance measurements alongside inelastic neutron scattering (INS) to study NCTO’s quantum magnetism, and we have found a field-induced spin disordered state in an applied magnetic field range of 7.5 T < B (⊥ b-axis) < 10.5 T. The INS spectra were also simulated to tentatively extract the exchange interactions. As a 3d-magnet with a field-induced disordered state on an effective spin-1/2 honeycomb lattice, NCTO expands the Kitaev model to 3d compounds, promoting further interests on the spin-orbital effect in quantum magnets.

scholarly journals The investigation of Neutron Scattering In Spin Waves Theory of Ferromagnetic Crystals

2014 ◽  
Vol 8 (4) ◽  
Author(s):  
Azadeh Farzaneh ◽  
Mohammad Reza Abdi ◽  
Khadije Rezaee Ebrahim Saraee
Keyword(s):  
Neutron Scattering ◽  
Spin Wave ◽  
Cross Section ◽  
Inelastic Neutron Scattering ◽  
Spin Waves ◽  
Wave Theory ◽  
Spin Correlation ◽  
Inelastic Neutron ◽  
Magnetic Behaviour ◽  
Spin Interaction

Inelastic neutron scattering, probing the temporal spin-spin correlation at the different microscopic scale, is a powerful technique to study the magnetic behaviour of ferromagnetic crystals. In addition, high penetration power of neutron in samples has made it as a useful way for spin-spin interaction in neutron scattering. Changes in the magnetic cross section in term of different energy transfer and temperatures are calculated for nickel and iron as transition metals in Heisenberg model versus spin wave theory by considering atomic form factor. Finally, the effect of magnetic structure and behaviour of crystal in measuring cross-section shows that increasing temperature results in the Cross-section increase Also, the existence of propagating spin waves below Tc is compared in Ni and Fe in different momentum transfers. The relation of spin wave energy with temperature dependence of nickel has created different behaviour in the changes of cross section rather than iron.

scholarly journals Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Seung-Hwan Do ◽  
Hao Zhang ◽  
Travis J. Williams ◽  
Tao Hong ◽  
V. Ovidiu Garlea ◽  
...  
Keyword(s):  
Inelastic Neutron Scattering ◽  
Longitudinal Mode ◽  
Wave Theory ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Many Body ◽  
Longitudinal Modes ◽  
Quantum Magnet ◽  
Energy Mode ◽  
The Many

AbstractAn ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba2FeSi2O7 reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode.

EXACT SOLUTIONS IN A SPATIALLY ANISOTROPIC QUANTUM SPIN LADDER MODEL HAVING TWO- AND FOUR-SPIN EXCHANGE INTERACTIONS

2009 ◽  
Vol 23 (08) ◽  
pp. 1981-2019 ◽  
Author(s):  
J. H. BARRY ◽  
J. D. COHEN ◽  
M. W. MEISEL
Keyword(s):  
Spin Exchange ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Elementary Excitation ◽  
Quantum Spin ◽  
Quantum Model ◽  
Spin Ladder ◽  
Zero Field ◽  
Ladder Model

We consider a two-leg S=1/2 quantum spin ladder model with two-spin (intra-rung) and four-spin (inter-rung) Heisenberg exchange interactions and a uniform magnetic field. Exact mappings are derived connecting the partition function and correlations in the three-parameter quantum model to those known in a two-parameter Ising chain. The quantum phase diagram of the ladder magnet is determined. Static correlations provide pertinent correlation lengths and underlie spatial fluctuation behaviors at arbitrary temperatures, including quantum fluctuations at absolute zero. Dynamic correlations in zero field are used to obtain an exact solution for the inelastic neutron scattering function Sxx(q, ω) at all temperatures, explicitly yielding the elementary excitation spectrum.

Two Methods to Study Inelastic Neutron-Scattering Measurements Based on ωn(q) versus S(q, ω) Applied to the Magnetic Open Honeycomb Lattice Material Tb2Ir3Ga9

2022 ◽  
Author(s):  
R S Fishman ◽  
George Ostrouchov ◽  
Feng Ye
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Weighted Average ◽  
Inelastic Neutron ◽  
Honeycomb Lattice ◽  
Frequency Space ◽  
Advantages And Disadvantages ◽  
Scattering Spectrum ◽  
Instrumental Resolution ◽  
The Difference

Abstract This work describes two methods to fit the inelastic neutron-scattering spectrum S(q, ω) with wavector q and frequency ω. The common and well-established method extracts the experimental spin-wave branches ωn(q) from the measured spectra S(q ,ω) and then minimizes the difference between the observed and predicted frequencies. When n branches of frequencies are predicted but the measured frequencies overlap to produce only m < n branches, the weighted average of the predicted frequencies must be compared to the observed frequencies. A penalty is then exacted when the width of the predicted frequencies exceeds the width of the observed frequencies. The second method directly compares the measured and predicted intensities S(q ,ω) over a grid {q i , ωj} in wavevector and frequency space. After subtracting background noise from the observed intensities, the theoretical intensities are scaled by a simple wavevector-dependent function that reflects the instrumental resolution. The advantages and disadvantages of each approach are demonstrated by studying the open honeycomb material Tb2Ir3Ga9.

Magnetic diffuse and small-angle scattering

1980 ◽  
Vol 290 (1043) ◽  
pp. 527-535 ◽  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Inelastic Neutron ◽  
Small Angle Scattering ◽  
Relaxation Processes ◽  
Magnetic Systems ◽  
Angle Scattering ◽  
Disordered Magnetic

Magnetic neutron scattering is one of the most valuable tools in exploring magnetism. For disordered magnetic systems, in addition to Bragg scattering, diffuse and small-angle scattering give information. Experimental techniques of the two last mentioned methods are described. They succeeded in a microscopic explanation of magnetic alloys with paramagnetic, spin-glass, ferromagnetic and antiferromagnetic character. Typical examples will be discussed in detail. Non-frozen local magnetic moments show quasi-elastic scattering, the half-width of which is a characteristic for the relaxation processes. By diffuse inelastic neutron scattering the temperature dependence and concentration dependence of such relaxation processes have been studied for classical paramagnetic, Kondo- and intermediate-valence systems. An additional impact to the field is to be expected from new developments of polarization analysis techniques.

scholarly journals Investigating ultrafast quantum magnetism with machine learning

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Giammarco Fabiani ◽  
Johan Mentink
Keyword(s):  
Quantum Monte Carlo ◽  
Large Scale ◽  
Spin Dynamics ◽  
Wave Theory ◽  
Quantum Spin ◽  
Square Lattice ◽  
Quantum Magnetism ◽  
Many Body ◽  
Static Properties ◽  
Body Dynamics

We investigate the efficiency of the recently proposed Restricted Boltzmann Machine (RBM) representation of quantum many-body states to study both the static properties and quantum spin dynamics in the two-dimensional Heisenberg model on a square lattice. For static properties we find close agreement with numerically exact Quantum Monte Carlo results in the thermodynamical limit. For dynamics and small systems, we find excellent agreement with exact diagonalization, while for systems up to N=256 spins close consistency with interacting spin-wave theory is obtained. In all cases the accuracy converges fast with the number of network parameters, giving access to much bigger systems than feasible before. This suggests great potential to investigate the quantum many-body dynamics of large scale spin systems relevant for the description of magnetic materials strongly out of equilibrium.

scholarly journals Suppressed-moment 2-k order in the canonical frustrated antiferromagnet Gd2Ti2O7

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Joseph A. M. Paddison ◽  
Georg Ehlers ◽  
Andrew B. Cairns ◽  
Jason S. Gardner ◽  
Oleg A. Petrenko ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Spin Wave ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Thermal Fluctuation ◽  
Inelastic Neutron ◽  
Scattering Measurements ◽  
Theoretical Predictions ◽  
Powder Samples

AbstractIn partially ordered magnets, order and disorder coexist in the same magnetic phase, distinct from both spin liquids and spin solids. Here, we determine the nature of partial magnetic ordering in the canonical frustrated antiferromagnet Gd2Ti2O7, in which Gd3+ spins occupy a pyrochlore lattice. Using single-crystal neutron-diffraction measurements in applied magnetic field, magnetic symmetry analysis, inelastic neutron-scattering measurements, and spin-wave modeling, we show that its low-temperature magnetic structure involves two propagation vectors (2-k structure) with suppressed ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental results are consistent with theoretical predictions of thermal fluctuation-driven order in Gd2Ti2O7, and reveal that inelastic neutron-scattering measurements on powder samples can solve the longstanding problem of distinguishing single-k and multi-k magnetic structures.

scholarly journals Thermodynamics and Magnetic Excitations in Quantum Spin Trimers: Applications for the Understanding of Molecular Magnets

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 93 ◽  
Author(s):  
Amelia Brumfield ◽  
Jason Haraldsen
Keyword(s):  
Spin Exchange ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Quantum Spin ◽  
Molecular Magnets ◽  
Molecular Magnet ◽  
Magnetic Excitations ◽  
Structure Factors ◽  
Coupling Parameters ◽  
The Individual

Molecular magnets provide a playground of interesting phenomena and interactions that have direct applications for quantum computation and magnetic systems. A general understanding of the underlying geometries for molecular magnets therefore generates a consistent foundation for which further analysis and understanding can be established. Using a Heisenberg spin-spin exchange Hamiltonian, we investigate the evolution of magnetic excitations and thermodynamics of quantum spin isosceles trimers (two sides J and one side α J ) with increasing spin. For the thermodynamics, we produce exact general solutions for the energy eigenstates and spin decomposition, which can be used to determine the heat capacity and magnetic susceptibility quickly. We show how the thermodynamic properties change with α coupling parameters and how the underlying ground state governs the Schottky anomaly. Furthermore, we investigate the microscopic excitations by examining the inelastic neutron scattering excitations and structure factors. Here, we illustrate how the individual dimer subgeometry governs the ability for probing underlying excitations. Overall, we feel these calculations can help with the general analysis and characterization of molecular magnet systems.

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