Magnetic excitations in the quantum spin system<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">TlCuCl</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Cavadini, N.; Heigold, G; Henggeler, W.; Furrer, A.; Güdel, Hans‐Ulrich; Krämer, Karl; Mutka, H.

doi:10.1103/physrevb.63.172414

Cited by 125 publications

(156 citation statements)

References 25 publications

Supporting

Mentioning

145

Contrasting

Order By: Relevance

“…2 In these case, antiferromagnetic order perpendicular to the field appears simultaneously with magnetization parallel to the field, creating field-induced magnetic order, 6 which can be interpreted as a condensation of the lowest lying magnon mode. 7,8,9,10,11,12,13,14,15 In contrast to these case, when the interaction energy dominates, magnetization plateaus can appear accompanied by a magnetic superlattice. 16 Such plateaus have been observed at a rational fraction of the saturation moment.…”

mentioning

confidence: 87%

Microscopic model for the magnetization plateaus inNH4CuCl3

Matsumoto

2003

Phys. Rev. B

View full text Add to dashboard Cite

A simple model consisting of three distinct dimer sublattices is proposed to describe the magnetism of NH4CuCl3. It explains the occurrence of magnetization plateaus only at 1/4 and 3/4 of the saturation magnetization. The field dependence of the excitation modes observed by ESR measurements is also explained by the model. The model predicts that the magnetization plateaus should disappear under high pressure.PACS numbers: 75.30. Cr, NH 4 CuCl 3 , TlCuCl 3 , and KCuCl 3 are isostructual quantum spin systems consisting of two-leg ladders separated by NH + 4 , Tl + , and K + ions. The two-leg ladders are composed of Cu 2+ ions with spin S = 1/2 which interact antiferromagnetically (AF) through the Cl − ions. These compounds can be considered as coupled two-leg S = 1/2 Heisenberg AF spin ladders, and show various types of magnetization curves. Shiramura et al. found that NH 4 CuCl 3 has magnetization plateaus at 1/4 and 3/4 of the saturation moment, 1 while TlCuCl 3 and KCuCl 3 have no plateaus in their magnetization curves. 2 For NH 4 CuCl 3 , Kurniawan et al. performed ESR experiments which revealed that NH 4 CuCl 3 has a finite excitation gap in the plateau regions. 3 By studying specific heat, they found AF order already at zero field and suggested a phase diagram in finite fields containing three magnetically ordered phases. 4 The origin of magnetization plateaus has attracted much interest recently. For weakly interacting dimer systems, the ground state is a spin singlet liquid with only short-range correlations between spins, and the triplet excitations require a finite excitation energy. An excited gas of triplet magnons has two characteristic energies. 5 Exchange interactions cause the transfer of excited triplets between neighboring dimers leading to a form of kinetic energy. They also lead to a short range repulsion between triplets in addition to the hard core repulsion forbidding double occupancy of a dimer. The triplet excitations are split in an external magnetic field, and the energy of the lowest component can be driven through zero. When the kinetic energy is dominant, which is realized in TlCuCl 3 and KCuCl 3 , we have no plateaus in the magnetization curve. 2 In these case, antiferromagnetic order perpendicular to the field appears simultaneously with magnetization parallel to the field, creating field-induced magnetic order, 6 which can be interpreted as a condensation of the lowest lying magnon mode. 7,8,9,10,11,12,13,14,15 In contrast to these case, when the interaction energy dominates, magnetization plateaus can appear accompanied by a magnetic superlattice. 16 Such plateaus have been observed at a rational fraction of the saturation moment. 1,17 In SrCu 2 (BO 3 ) 2 , the frustrated form of the dimer lattice leads to a narrow bandwidth for triplet excitations and magnetization plateaus associated with a magnetic superlattice of localized triplets. 18,19 An unexpected feature of NH 4 CuCl 3 is the absence of a magnetization plateau at a value 1/2 of the saturation magnetization although this...

show abstract

mentioning

confidence: 87%

Microscopic model for the magnetization plateaus inNH4CuCl3

Matsumoto

2003

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…The agreement between the TTW-MF result and the experimental data is excellent over the full temperature range of the investigation. We stress that no free parameters are introduced with respect to the lowtemperature dispersion [5,13].…”

Section: -2mentioning

confidence: 99%

“…Only in the high-temperature limit, relative to the intradimer exchange constant J 56 K [5,13], is the system better described in terms of S 1=2 fermions whose interactions are weak compared to the thermal fluctuations, and AF dimer correlations are strongly suppressed. In the intermediate regime, < T < J, a singlet-triplet description remains valid but the number of excited triplets becomes significant.…”

mentioning

confidence: 99%

“…While control parameters such as the magnetic field or applied pressure may seem rather abstract by comparison, in certain classes of system they have a profound effect on the quantum mechanical fluctuations of the dominant degrees of freedom. In this respect, dimer spin systems such as BaCuSi 2 O 6 [2 -4], TlCuCl 3 [5][6][7][8][9], and Cs 3 Cr 2 Br 9 [10] have recently attracted considerable attention as they exhibit both field-and (in TlCuCl 3 ) pressure-induced magnetic quantum phase transitions. The ordered phases have also been described as a novel state resulting from BoseEinstein condensation of magnons [11,12].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Quantum Statistics of Interacting Dimer Spin Systems

et al. 2005

Self Cite

View full text Add to dashboard Cite

The compound TlCuCl 3 represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron scattering experiments on single crystals. By comparison with a number of theoretical approaches we demonstrate that the description of Troyer, Tsunetsugu, and Würtz [Phys. Rev. B 50, 13 515 (1994)] provides an appropriate quantum statistical model for dimer spin systems at finite temperatures, where many-body correlations become particularly important. DOI: 10.1103/PhysRevLett.95.267201 PACS numbers: 75.10.Jm, 05.30.Jp, 78.70.Nx The temperature is without doubt the key control parameter in solid-state physics, for both historical and technical reasons. Historically, the study of thermal fluctuations created the discipline of statistical mechanics. As one technical example, the liquefaction of helium in 1908 enabled the discovery of superconductivity in 1911 [1]. While control parameters such as the magnetic field or applied pressure may seem rather abstract by comparison, in certain classes of system they have a profound effect on the quantum mechanical fluctuations of the dominant degrees of freedom. In this respect, dimer spin systems such as BaCuSi 2 O 6 [2 -4], TlCuCl 3 [5-9], and Cs 3 Cr 2 Br 9 [10] have recently attracted considerable attention as they exhibit both field-and (in TlCuCl 3 ) pressure-induced magnetic quantum phase transitions. The ordered phases have also been described as a novel state resulting from BoseEinstein condensation of magnons [11,12].To date, the primary experimental and theoretical studies of these systems have focused on elucidating the parameter dependence of the ground and excited states at ''T 0 K' ' [3,4,6 -10]. However, the temperature dependence of the spin-spin correlation function S Q; ! in such dimer-based compounds is also of fundamental interest. At finite temperatures, thermal fluctuations populating the excited triplet states above the energy gap, 7:5 K, in the spin excitation spectrum of TlCuCl 3 become significant and compete with the intrinsic quantum fluctuations. The absence of a classical ordering transition in zero field and at ambient pressure, and the strong interdimer interactions, make TlCuCl 3 an ideal candidate for an experimental investigation of the quantum statistical description for such a spin system.In TlCuCl 3 , the antiferromagnetic (AF) dimer unit is formed by the two S 1=2 magnetic moments in a pair of Cu 2 ions, and has a singlet ground state (total spin S 0) with triplet (S 1) excited states which may be considered as bosonic quasiparticles. Only in the high-temperature limit, relative to the intradimer exchange constant J 56 K [5,13], is the system better described in terms of S 1=2 fermions whose interactions are weak compared to the thermal fluctuations, and AF dimer correlations are strongly suppressed. In the intermediate regime, < T < J, a singlet-triplet description remains valid but the number of excited triplets becomes significan...

show abstract

“…From the analyses of the dispersion relations obtained by neutron inelastic scattering experiments, it was found that the origin of the spin gap is the strong antiferromagnetic interaction in the chemical dimer Cu 2 Cl 6 , and that the neighboring dimers are coupled by the interdimer interactions along the double chain and in the (1, 0, −2) plane [13,14,15,16,17]. On the other hand, NH 4 CuCl 3 is a gapless antiferromagnet with T N = 1.3 K [18].…”

mentioning

confidence: 99%

C63/65u- andC35/

et al. 2009

View full text Add to dashboard Cite

63/65 Cu-and 35/37 Cl-NMR experiments were performed to investigate triplet localization in the S = 1/2 dimer compound NH 4 CuCl 3 , which shows magnetization plateaus at one-quarter and three-quarters of the saturation magnetization. In 63/65 Cu-NMR experiments, signal from only the singlet Cu site was observed, because that from the triplet Cu site was invisible due to the strong spin fluctuation of onsite 3d-spins. We found that the temperature dependence of the shift of 63/65 Cu-NMR spectra at the singlet Cu site deviated from that of macroscopic magnetization below T = 6 K. This deviation is interpreted as the triplet localization in this system. From the 35/37 Cl-NMR experiments at the 1/4-plateau phase, we found the two different temperature dependences of Cl-shift, namely the temperature dependence of one deviates below T = 6 K from that of the macroscopic magnetization as observed in the 63/65 Cu-NMR experiments, whereas the other corresponds well with that of the macroscopic magnetization in the entire experimental temperature region. We interpreted these dependences as reflecting the transferred hyperfine field at the Cl site located at a singlet site and at a triplet site, respectively. This result also indicates that the triplets are localized at low temperatures. 63/65 Cu-NMR experiments performed at high magnetic fields between the one-quarter and three-quarters magnetization plateaus have revealed that the two differently oriented dimers in the unit cell are equally occupied by triplets, the fact of which limits the theoretical model on the periodic structure of the localized triplets.

show abstract

Magnetic excitations in the quantum spin systemTlCuCl3

Cited by 125 publications

References 25 publications

Microscopic model for the magnetization plateaus inNH4CuCl3

Microscopic model for the magnetization plateaus inNH4CuCl3

Quantum Statistics of Interacting Dimer Spin Systems

C63/65u- andC35/

Contact Info

Product

Resources

About