Anisotropic Propagating Excitations and Quadrupolar Effects in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Tb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Ti</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="bold">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:math>

Guitteny, S.; Robert, J.; Bonville, P.; Ollivier, Jacques; Decorse, Claudia; Steffens, P.; Boehm, Martin; Mutka, H.; Mirebeau, I.; Petit, S.

doi:10.1103/physrevlett.111.087201

Cited by 70 publications

(104 citation statements)

References 59 publications

(126 reference statements)

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“…These findings should now be confronted to recent studies in single crystals 4,28,30 . In single crystals, the temperature variation of the diffuse scattering shows a gradual evolution from a fluctuating spin liquid state characterized by isotropic first neighbor correlations at high temperatures, to a precursor regime (between T G and 4 K typically) where the diffuse scattering starts to be structured and the elastic component increases steadily, then to a regime (T< T G ) where the elastic signal is dominant, well structured and T-independent.…”

Section: Discussionmentioning

confidence: 99%

“…In the "spin liquid" samples below x c which show no anomaly of C p (T ), the magnetic order would remain limited to short length scales. Below T G the elastic diffuse scattering measured on single crystals 4,28,30 shows arm-like features along 111 directions and butterfly shaped features centered at (002) and (220). These features result in diffuse maxima around ( 1 2 , 1 2 , 1 2 ) positions and equivalent (see Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Several mechanisms have been proposed taking into account the non-Kramers nature of the Tb ion and the small energy gap between the ground and first excited crystal field doublets, which open the possibility of quantum spin ice behavior 19 . Recent studies of the crystal and magnetic excitations using polarized neutrons show that the magneto-elastic coupling plays a crucial role, yielding an interaction between the first excited crystal field level and an acoustic phonon branch, resulting in a hybrid phonon-magnon mode 4,5 . The magnetoelastic coupling also induces original properties in the pyrochlore family, such as giant magnetostriction 20,21 and very low thermal conductivity 22 .…”

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confidence: 99%

“…The short range ordered ground states with large degeneracy give rise to a large variety of interesting phenomena such as magnetic monopoles 1,2 , first order transition 3 , or unconventional magnetoelastic excitations 4,5 . These frustrated ground states are highly sensitive to small perturbations and to the presence of defects.…”

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confidence: 99%

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Mesoscopic correlations inTb2Ti2O7spin liquid

et al. 2015

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We have studied the spin correlations with k= ( 1 2 , 1 2 , 1 2 ) propagation vector which appear below 0.4 K in Tb2Ti2O7 spin liquid by combining powder neutron diffraction and specific heat on Tb2+xTi2−xO7+y samples with x=0, 0.01, -0.01. The k= ( 1 2 , 1 2 , 1 2 ) order clearly appears on all neutron patterns by subtracting a pattern at 1.2(1) K. Refining the subtracted patterns at 0.07 K yields two possible spin structures, with spin-ice-like and monopole-like correlations respectively. Mesoscopic correlations involve Tb moments of 1 to 2 µB ordered on a length scale of about 20Å. In addition, long range order involving a small spin component of 0.1 to 0.2 µB is detected for the x= 0 and 0.01 samples showing a peak in the specific heat. Comparison with previous single crystals data suggests that the ( 1 2 , 1 2 , 1 2 ) order settles in through nanometric spin textures with dominant spin ice character and correlated orientations, analogous to nanomagnetic twins.Rare earth pyrochlores with geometrical magnetic frustration are model compounds to investigate classical spin ice as well as quantum spin ice physics. The short range ordered ground states with large degeneracy give rise to a large variety of interesting phenomena such as magnetic monopoles 1,2 , first order transition 3 , or unconventional magnetoelastic excitations 4,5 . These frustrated ground states are highly sensitive to small perturbations and to the presence of defects. Already in the 80s, Villain 6 predicted that for an arbitrary small concentration of defects the spinel lattice with pyrochlore structure could switch its ground state from spin liquid to spin glass. More recently many studies focus on the role of a minute amount of defects in pyrochlores. The crystal structure of R 2 Ti 2 O 7 pyrochlores (where R 3+ is a rare earth ion, Ti 4+ is non magnetic) accommodates oxygen vacancies, small off-stoechiometries in the R 3+ or Ti 4+ lattice, "stuffing" or site inversion. Oxygen vacancies introduce Ti 3+ defects instead of Ti 4+ ions, modifying the R 3+ crystal field and inducing local distortions, with various consequences on the low temperature magnetic properties and spin ice physics. In classical spin ice Dy 2 Ti 2 O 7 , oxygen depletion or a low level Dy stuffing in the Ti sites strongly slows down the monopole dynamics at very low temperature 7,8 and affects the nonequilibrium macroscopic properties 9,10 . In the quantum spin ice Yb 2 Ti 2 O 7 , small off-stoechiometry clearly affects the magnetic ground state 11 . It appears that precise studies of the magnetic defects are needed to resolve controversies concerning these unconventional ground states.Among the pyrochlores, Tb 2 Ti 2 O 7 is one of the most complex, the subject of numerous investigations since the discovery of its spin liquid character in 1999. The Tb 3+ short range correlated moments fluctuate 12 down to 20 mK at the time scale of the muon probe (10 −6 s). The origin of these fluctuations has been highly debated [13][14][15][16][17][18] . Several mechanisms have been pr...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Mesoscopic correlations inTb2Ti2O7spin liquid

et al. 2015

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“…Remarkably, the ground state supports elastic power law spin correlations [17,18], bearing some resemblance to the pinch point pattern observed in spin ices [19]. Below 300 mK, a dispersing low-energy collective mode is found to emerge from these pinch points, reaching its maximum energy at ∼0.25 meV [20]. This signal likely corresponds to fluctuations between the two |± electronic states of the crystal electric field (CEF) ground state doublet.…”

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Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

et al. 2017

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The origin of quantum fluctuations responsible for the spin liquid state in Tb2Ti2O7 has remained a long standing problem. By synchrotron-based terahertz measurements, we show evidence of strong coupling between the magnetic and lattice degrees of freedom that provides a path to the quantum melting process. As revealed by hybrid crystal electric field-phonon excitations that appear at 0.67 THz below 200 K, and around 0.42 THz below 50 K, the double vibronic process is unique for Tb 3+ in the titanate family due to adequate energy matching and strong quadrupolar moments. The results suggest that lattice motion can indeed be the driving force behind spin flips within the hybridized ground and first excited states, promoting quantum terms in the effective Hamiltonian that describes Tb2Ti2O7.Keywords: THz spectroscopy, pyrochlore, frustration, spin-lattice coupling Over the last decade, spin-ice physics has aroused significant attention [1, 2]. It emerges in pyrochlore magnets, such as Ho 2 Ti 2 O 7 or Dy 2 Ti 2 O 7 , as a result of effective ferromagnetic interactions coupling the Ising-like rare-earth magnetic moments constrained along the local 111 directions by the crystal field [3][4][5] (Fig. 1 (a,b)). This combination impedes long-range order, favoring a disordered and macroscopically degenerate magnetic state governed by an organizing principle, the socalled "ice rule," where two spins point into and two out of each elementary tetrahedron in the structure [3].The possibility that quantum fluctuations can melt the spin ice state is a topical issue. It is expected to lead to a wealth of exotic phenomena such as a quantum superposition of "two-in two-out" configurations and emergent electrodynamics with new deconfined particles [6][7][8][9][10][11].In this context, the puzzling behavior of the spin liquid Tb 2 Ti 2 O 7 has attracted much attention. Despite effective antiferromagnetic interactions, Tb 2 Ti 2 O 7 features no long-range order [12,13], however short-range correlations are present over a broad temperature range [14][15][16]. Remarkably, the ground state supports elastic power law spin correlations [17,18], bearing some resemblance to the pinch point pattern observed in spin ices [19]. Below 300 mK, a dispersing low-energy collective mode is found to emerge from these pinch points, reaching its maximum energy at ∼0.25 meV [20]. This signal likely corresponds to fluctuations between the two |± electronic states of the crystal electric field (CEF) ground state doublet. It was interpreted as a signature of interactions between quadrupoles, highlighting the importance of those degrees of freedom [18,[20][21][22]. This is because the non-Kramers nature of Tb 3+ ions prevents magnetic exchange alone from inducing such fluctuations within the Ising-like ground state [22][23][24].A property that distinguishes Tb 2 Ti 2 O 7 from the other rare-earth titanates is the CEF energy spectrum of Tb 3+ . It features a first excited doublet at a low energy of ∆ ≈ 1.5 meV above the ground state [25][26][27][28][29], ...

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Experimental Search for Quantum Spin Ice

Ross

2021

Springer Series in Solid-State Sciences

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Anisotropic Propagating Excitations and Quadrupolar Effects inTb2Ti2O7

Cited by 70 publications

References 59 publications

Mesoscopic correlations inTb2Ti2O7spin liquid

Mesoscopic correlations inTb2Ti2O7spin liquid

Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

Experimental Search for Quantum Spin Ice

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