Extended Universal Finite-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>T</mml:mi></mml:math>Renormalization of Excitations in a Class of One-Dimensional Quantum Magnets

Zheludev, A.; Garlea, V. Ovidiu; Regnault, L.P.; Manaka, Hirotaka; Tsvelik, A. M.; Chung, Jaiho

doi:10.1103/physrevlett.100.157204

Cited by 40 publications

(56 citation statements)

References 29 publications

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“…They all agree very well with experimental data [9,23,[31][32][33] which supports the advocated model. Since the characterization of IPA-CuCl 3 by Roberts et al [25] various spin models were discussed.…”

Section: P-1supporting

confidence: 79%

“…This implies a dependence of the dispersion on s and hence on temperature [40,52,54], denoted by ω s(T ) (h, l). The self-consistent solution is found from the hardcore condition 1 = s † r s r + m t † m,r t m,r leading to s 2 (T ) = 1 − 3z/(1 + 3z) with Figure 5 compares the result (solid line) of this simple approximation to INS data [32,33]. Up to 15 K the experimental data is matched perfectly.…”

Section: P-1mentioning

confidence: 50%

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Microscopic model for Bose-Einstein condensation and quasiparticle decay

Fischer¹,

Duffe²,

Uhrig³

2011

EPL

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Abstract. -Sufficiently dimerized quantum antiferromagnets display elementary S = 1 excitations, triplon quasiparticles, protected by a gap at low energies. At higher energies, the triplons may decay into two or more triplons. A strong enough magnetic field induces Bose-Einstein condensation of triplons. For both phenomena the compound IPA-CuCl3 is an excellent model system. Nevertheless no quantitative model was determined so far despite numerous studies. Recent theoretical progress allows us to analyse data of inelastic neutron scattering (INS) and of magnetic susceptibility to determine the four magnetic couplings J1 ≈ −2.3 meV, J2 ≈ 1.2 meV, J3 ≈ 2.9 meV and J4 ≈ −0.3 meV. These couplings determine IPA-CuCl3 as system of coupled asymmetric S = 1/2 Heisenberg ladders quantitatively. The magnetic field dependence of the lowest modes in the condensed phase as well as the temperature dependence of the gap without magnetic field corroborate this microscopic model.Low-dimensional antiferromagnetic quantum spin systems display various fascinating properties, e.g., spinPeierls transition [1, 2], appearance of a Haldane gap for integer spins [3,4], high-temperature superconductivity upon doping [5], and the Bose-Einstein condensation (BEC) in spin-dimer systems [6][7][8][9], where the latter one is characterized by a phase transition from a non-magnetic phase to a long-range antiferromagnetically ordered gapless phase at a critical magnetic field H c1 .Another fascinating phenomenon recently observed in low-dimensional antiferromagnets is the decay of their elementary S = 1 excitations, triplons [10], at higher energies so that the triplons exist only in a restricted part of the Brillouin zone [11,12]. Theoretically as well, there is rising interest in the understanding and quantitative description of this phenomenon for gapped triplons [13][14][15][16] as well as for gapless magnons [17][18][19].The description of quasiparticle decay faces an intrinsic difficulty. The merging of the long-lived, infinitely sharp elementary triplon with a multitriplon continuum requires to describe the resulting resonance and its edges precisely. This is still a challenge for numerical approaches such as exact diagonalization or dynamic density-matrix (a) fischer@fkt.physik.tu-dortmund.de (b) goetz.uhrig@tu-dortmund.de renormalization [20]. Diagrammatic approaches are able to capture the qualitative features but may encounter difficulties in the quantitative description in the regime of strong merging where the sharp mode dissolves completely in the continuum because this is a strong coupling phenomenon [13,14]. Unitary transformations also face difficulties when modes of finite life-time occur [16].A crucial step in the understanding of both phenomena is to identify a suitable experimental system. The best studied candidate for the BEC in coupled spin-dimer systems is TlCuCl 3 . Unfortunately, recent research suggests that the high field spectrum remains gapped [21,22] in contrast to what is expected from a phase where a continuous s...

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Section: P-1supporting

confidence: 79%

Section: P-1mentioning

confidence: 50%

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Fischer¹,

Duffe²,

Uhrig³

2011

EPL

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“…The inwards renormalization of the dispersion occurs because as temperature is increased the dimers become thermally excited which interferes with the intersite interactions, thus the dispersion tends towards the intradimer exchange energy J 0 . Such a renormalization has been reported previously for other gapped dimer antiferromagnets [16] 19]. The strong decrease in integrated intensity of the mode at (0, 0, 3) h is shown in Fig.…”

supporting

confidence: 86%

Asymmetric Thermal Line Shape Broadening in a Gapped 3D Antiferromagnet: Evidence for Strong Correlations at Finite Temperature

et al. 2012

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It is widely believed that magnetic excitations become increasingly incoherent as temperature is raised due to random collisions which limit their lifetime. This picture is based on spin-wave calculations for gapless magnets in 2 and 3 dimensions and is observed experimentally as a symmetric Lorentzian broadening in energy. Here, we investigate a three-dimensional dimer antiferromagnet and find unexpectedly that the broadening is asymmetric -indicating that far from thermal decoherence, the excitations behave collectively like a strongly correlated gas. This result suggests that a temperature activated coherent state of quasi-particles is not confined to special cases like the highlydimerized spin-1/2 chain but is found generally in dimerized antiferromagnets of all dimensionalities and perhaps gapped magnets in general.PACS numbers: 75.10. Jm, 03.75.Kk, 03.75.Gg, 78.70.Nx In the conventional picture of temperature effects in magnetism, the excitations are long-lived at low temperatures and their lifetime decreases as temperature is increased. The accepted reason for this is that thermally activated excitations collide with each other limiting their lifetimes which results in a Lorentzian energy broadening of the lineshapes [1,2]. This model works well for gapless magnets with long-range magnetic order. Experimental investigations of the two-dimensional (2D) and three-dimensional (3D), gapless spin−5/2 (S−5/2), Heisenberg antiferromagnets (HAF) Rb 2 MnF 4 [3] and MnF 2 [4] reveal symmetric Lorentzian lineshapes which broaden with temperature in excellent agreement with spin-wave calculations [1,2]. The basic assumption behind this description is that the spin-waves interact only weakly and the states available to them cover an extensive region of phase space. As the population of excited spin-waves increases with temperature, the rate of collisions between them also increases and they fluctuate within this large range of states in an uncorrelated manner. The damping is then due simply to loss of coherence associated with the reduced lifetime of the excitations.The concept of thermal decoherence and the associated Lorentzian linewidth broadening have become so entrenched in current thinking that it is generally assumed to apply to all magnetic systems [5,6]. However for some magnets where there are strong interactions between the excitations and the phase space is restricted, it is not obvious that this reasoning should apply. Gapped antiferromagnets such as Haldane chains, spin ladders and dimer magnets which have a singlet ground state and triplet excitations are potential candidates. For the S-1/2, dimer HAFs a dominant antiferromagnetic exchange interaction J 0 , pairs the spins into dimers. The ground state is a singlet and the excited state is a triplet gapped by ≈J 0 while interdimer interactions allow the triplets to become dispersive and mobile. In the case of a large gap compared to the excitation bandwidth, the distribution of dimer excitations is severely limited. In addition, the dimers are subjec...

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“…Because of coupling between dimers, triplons usually become mobile and can hop to neighboring dimer sites. For particular cases, the thermodynamic finite temperature behavior of the mobility of these hard-core bosons has been treated using statistical models reproducing triplon band renormalization and damping observed in experiments [5][6][7][8][9]. In general, the increase of the thermal population of bosons produces an increased repulsion and a reduced mobility, which is observed as a reduction of the dispersion bandwidth.…”

mentioning

confidence: 99%

Correlated Decay of Triplet Excitations in the Shastry-Sutherland CompoundSrCu2(BO3)2
Zayed
¹
,
Rüegg
²
,
Strässle
³

et al. 2014
Phys. Rev. Lett.
19
2
19
0
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The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu 2 ðBO 3 Þ 2 is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature, while the integrated spectral weight can be explained by an isolated dimer model up to 10 K. Analyzing this anomalous spectral line shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long lived if no thermally populated triplons are nearby but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry-Sutherland lattice. Quantum spin systems display a wide range of intriguing many-body quantum effects. A particularly active field is the study of interacting dimer systems. Two antiferromagnetically coupled spins forming a dimer have a singlet ground state with an energy gap to excited triplet states. In extended systems where dimers couple to each other, the ground state often remains a spin singlet and gapped. The excitations are known as triplons and can be described in terms of quasiparticles as hard-core bosons [1][2][3][4]. Because of coupling between dimers, triplons usually become mobile and can hop to neighboring dimer sites. For particular cases, the thermodynamic finite temperature behavior of the mobility of these hard-core bosons has been treated using statistical models reproducing triplon band renormalization and damping observed in experiments [5][6][7][8][9]. In general, the increase of the thermal population of bosons produces an increased repulsion and a reduced mobility, which is observed as a reduction of the dispersion bandwidth. The theoretical treatment of finite temperature damping, reflecting the lifetime of the boson and the related spectral functions, remains an ongoing challenge [10][11][12][13].The compound SrCu 2 ðBO 3 Þ 2 constitutes an important example for testing our understanding of quantum spin systems, as it is a close realization of the frustrated but "exactly solvable" 2D Shastry-Sutherland model [14,15] (see Refs. [16,17] for a review). In SrCu 2 ðBO 3 Þ 2 , triplons are prevented from hopping already at zero temperature by frustrated interdimer interactions. Despite the strong (frustrated) coupling, the triplon dispersion is very shallow. Theoretical studies show that hopping is allowed only from the sixth order in the inter-to intradimer coupling ratio J 0 =J or in the presence of Dzyaloshinskii-Moriya (DM) terms. It has, however, been shown that multiple triplons forming a bound state are more mobile than a single triplon due to correlated hopping processes, appearing already in second order in J 0 =J [16,18]. In high magnetic fields, triplons in SrCu 2 ðBO 3 Þ 2 crystalliz...

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Extended Universal Finite-TRenormalization of Excitations in a Class of One-Dimensional Quantum Magnets

Cited by 40 publications

References 29 publications

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Asymmetric Thermal Line Shape Broadening in a Gapped 3D Antiferromagnet: Evidence for Strong Correlations at Finite Temperature

Correlated Decay of Triplet Excitations in the Shastry-Sutherland CompoundSrCu2(BO3)2
Zayed
¹
,
Rüegg
²
,
Strässle
³

et al. 2014
Phys. Rev. Lett.
19
2
19
0
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Extended Universal Finite-TRenormalization of Excitations in a Class of One-Dimensional Quantum Magnets

Cited by 40 publications

References 29 publications

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Asymmetric Thermal Line Shape Broadening in a Gapped 3D Antiferromagnet: Evidence for Strong Correlations at Finite Temperature

Correlated Decay of Triplet Excitations in the Shastry-Sutherland CompoundSrCu2(BO3)2Zayed1, Rüegg2, Strässle3 et al. 2014Phys. Rev. Lett.192190View full textAdd to dashboardCite

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Correlated Decay of Triplet Excitations in the Shastry-Sutherland CompoundSrCu2(BO3)2
Zayed
¹
,
Rüegg
²
,
Strässle
³

et al. 2014
Phys. Rev. Lett.
19
2
19
0
View full text Add to dashboard Cite