Quantum magnetic interactions inS= 1/2 KCuCl3

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

doi:10.1088/0953-8984/12/25/310

Cited by 31 publications

(41 citation statements)

References 21 publications

(37 reference statements)

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“…[9][10][11][12]17,18) Since there are two different dimers per chemical unit cell, the triplet excitations have two branches ! AE ðQÞ.…”

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confidence: 99%

“…AE ðQÞ. Within the framework of the random phase approximation, the dispersion relations in the present system are expressed as [9][10][11][12]17,18) h " ! AE ðQÞ ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi…”

Section: )mentioning

confidence: 99%

“…1, neighboring spin dimers couple along the a-axis and in the ð1; 0; " 2 2Þ plane, in which the hole orbitals of Cu 2þ spread. [8][9][10][11][12] The lowest triplet excitation occurs at Q ¼ ð0; 0; 1Þ and its equivalent reciprocal points. The magnitude of the energy gap is Á ¼ 2:67 meV.…”

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confidence: 99%

“…The dashed lines in Fig. 4 denote the fits of the dispersion curves at ambient pressure [8][9][10][11][12] obtained using eq. (1) with the exchange parameters listed in Table I.…”

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Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃

et al. 2007

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KCuCl 3 is a three dimensionally coupled spin dimer system, which undergoes a pressure-induced quantum phase transition from a gapped ground state to an antiferromagnetic state at a critical pressure of P c ' 8:2 kbar. Magnetic excitations in KCuCl 3 at a hydrostatic pressure of 4.7 kbar have been investigated by conducting neutron inelastic scattering experiments using a newly designed cylindrical high-pressure clamp cell. A well-defined single excitation mode is observed. The softening of the excitation mode due to the applied pressure is clearly observed. From the analysis of the dispersion relations, it is found that an intradimer interaction decreases under hydrostatic pressure, while most interdimer interactions increase. For a system of isolated S ¼ 1=2 spin dimers with an antiferromagnetic (AF) intradimer exchange interaction J > 0, the triplet excitation is dispersionless and the excitation energy is given by h " !ðqÞ ¼ J. When a threedimensional interdimer exchange interaction J 0 is switched on, excited triplets can hop to neighboring dimers due to the transverse component of the interdimer interactionÞ so that the magnetic excitations become dispersive. With increasing ðJ 0 =JÞ, the dispersion range increases and the lowest excitation energy corresponding to the energy gap of the system decreases. At a quantum critical point ðJ 0 =JÞ c , the gap closes and the disordered ground state changes to the AF-ordered state. 1,2)The AF state stabilized for ðJ 0 =JÞ > ðJ 0 =JÞ c is described by the coherent superposition of the singlet j0; 0i and two triplet components j1; AE1i. Such a quantum phase transition (QPT) was first realized in TlCuCl 3 3-5) by the application of hydrostatic pressure. The critical pressures determined by magnetization measurement and neutron scattering experiment are P c ¼ 0:42 kbar 3) and 1.07 kbar, 5) respectively. There is a discrepancy between the critical pressures obtained from macroscopic and microscopic measurements.In this study, we investigate magnetic excitations in KCuCl 3 under hydrostatic pressure. The crystal structure (space group P2 1 =c) of KCuCl 3 is the same as that of TlCuCl 3 6,7) and is composed of planar dimers of Cu 2 Cl 6 . The dimers are stacked to form infinite double chains parallel to the crystallographic a-axis. These double chains are located at the corners and center of the unit cell in the bc-plane. A strong AF exchange interaction with J ¼ 4:34 meV in the planar dimer of Cu 2 Cl 6 dimerizes the spins of Cu 2þ . As shown in Fig. 1, neighboring spin dimers couple along the a-axis and in the ð1; 0; " 2 2Þ plane, in which the hole orbitals of Cu 2þ spread. [8][9][10][11][12] The lowest triplet excitation occurs at Q ¼ ð0; 0; 1Þ and its equivalent reciprocal points. The magnitude of the energy gap is Á ¼ 2:67 meV. 8,13,14) Consequently, KCuCl 3 is magnetically characterized as an interacting spin dimer system. KCuCl 3 undergoes a QPT under hydrostatic pressure, as observed in TlCuCl 3 .15) The critical pressure obtained through magnetization measurement ...

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“…[9][10][11][12]17,18) Since there are two different dimers per chemical unit cell, the triplet excitations have two branches ! AE ðQÞ.…”

Section: )mentioning

confidence: 99%

Section: )mentioning

confidence: 99%

mentioning

confidence: 99%

“…The dashed lines in Fig. 4 denote the fits of the dispersion curves at ambient pressure [8][9][10][11][12] obtained using eq. (1) with the exchange parameters listed in Table I.…”

mentioning

confidence: 99%

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Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃

et al. 2007

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“…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].…”

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confidence: 99%

C63/65u- andC35/

et al. 2009

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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.

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Introduction

Scammell¹

2018

Interplay of Quantum and Statistical Fluctuations in Critical Quantum Matter

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Quantum magnetic interactions inS= 1/2 KCuCl₃

Cited by 31 publications

References 21 publications

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃

C63/65u- andC35/

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Quantum magnetic interactions inS= 1/2 KCuCl3

Cited by 31 publications

References 21 publications

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl3

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl3

C63/65u- andC35/

Introduction

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Resources

About

Quantum magnetic interactions inS= 1/2 KCuCl₃

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃

Softening of Magnetic Excitations Leading to Pressure-Induced Quantum Phase Transition in Gapped Spin System KCuCl₃