Incommensurate dynamic correlations in the quasi-two-dimensional spin liquid BiCu<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>PO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>6</mml:mn></mml:msub></mml:math>

Plumb, K. W.; Yamani, Z.; Matsuda, M.; Shu, G. J.; Koteswararao, B.; Chou, F. C.; Kim, Yong Baek

doi:10.1103/physrevb.88.024402

Cited by 23 publications

(36 citation statements)

References 56 publications

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“…All measurements used the same 4.5 g single crystal as previous studies 28 . Magnetic excitations in BiCu 2 PO 6 were mapped through inelastic neutron scattering (INS) measurements performed on a number of instruments.…”

Section: Nature Physics Doi: 101038/nphys3566 Methodsmentioning

confidence: 99%

Quasiparticle-continuum level repulsion in a quantum magnet

et al. 2015

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*When the energy eigenvalues of two coupled quantum states approach each other in a certain parameter space, their energy levels repel each other and level crossing is avoided 1 . Such level repulsion, or avoided level crossing, is commonly used to describe the dispersion relation of quasiparticles in solids 2 . However, little is known about the level repulsion when more than two quasiparticles are present; for example, in a strongly interacting quantum system where a quasiparticle can spontaneously decay into a many-particle continuum [3][4][5] . Here we show that even in this case level repulsion exists between a long-lived quasiparticle state and a continuum. In our fine-resolution neutron spectroscopy study of magnetic quasiparticles in the frustrated quantum magnet BiCu 2 PO 6 , we observe a renormalization of the quasiparticle dispersion relation due to the presence of the continuum of multi-quasiparticle states.A fundamental concept in condensed matter physics is the idea that strongly interacting atomic systems can be treated as a collection of weakly interacting and long-lived quasiparticles. Within a quasiparticle picture, complex collective excited states in a many-body system are described in terms of effective elementary excitations. The quanta of these excitations carry a definite momentum and energy, and are termed quasiparticles. Magnetic insulators containing localized S = 1/2 magnetic moments and having valence-bond solid ground states are ideal systems in which to study bosonic quasiparticles in an interacting quantum many-body system 6 . The elementary magnetic excitations in these materials are triply degenerate S = 1 quasiparticles called triplons, and their momentum-and energy-resolved dynamics can be probed directly though inelastic neutron scattering (INS) measurements.In particular, when the system's Hamiltonian has an interaction term coupling single-particle and multi-particle states, the single quasiparticles may decay into the continuum of multi-particle states 3,4 . In such a system, the Hamiltonian for the single quasiparticles is non-Hermitian and the energy eigenvalues are in general complex. The single-particle decay typically occurs in two ways. Often the single-particle mode stays as a resonance inside the continuum, but the lifetime becomes short and the mode is highly damped 3 . Sometimes the single quasiparticle simply ceases to exist, and the dispersion abruptly terminates when it crosses the continuum boundary 5 . However, there is a third possibility, in which the single-quasiparticle dispersion is significantly renormalized to avoid the multi-particle continuum. This is analogous to the wellknown avoided level crossing behaviour of coupled modes, but in the complex plane of energy eigenvalues 7 . Despite broad interest in strongly interacting quantum systems, experimentally realizing an ideal condition to study the interaction between a quasiparticle and a multi-particle continuum turns out to be extremely difficult. One realization occurs in semiconducting quantum do...

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Section: Nature Physics Doi: 101038/nphys3566 Methodsmentioning

confidence: 99%

Quasiparticle-continuum level repulsion in a quantum magnet

et al. 2015

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“…These chains are coupled to one another along the c axis through another AF interaction J rung (≈58 K) to form a two-leg spin ladder in the bc plane121314. Various thermodynamic, light scattering and nuclear magnetic resonance measurements have indicated anisotropic spin-gap with the excitation energy (Δ/ k B ) ranging from 32 to 45 K, without any long-range spin order down to 0.1 K121314151617181920. The application of magnetic field then leads to reduction in the spin gap (Fig.…”

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Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6

Jeon

Koteswararao

Park

et al. 2016

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Thermal transport of quantum magnets has elucidated the nature of low energy elementary excitations and complex interplay between those excited states via strong scattering of thermal carriers. BiCu2PO6 is a unique frustrated spin-ladder compound exhibiting highly anisotropic spin excitations that contain both itinerant and localized dispersion characters along the b- and a-axes respectively. Here, we investigate thermal conductivity κ of BiCu2PO6 under high magnetic fields (H) of up to 30 tesla. A dip-feature in κ, located at ~15 K at zero-H along all crystallographic directions, moves gradually toward lower temperature (T) with increasing H, thus resulting in giant suppression by a factor of ~30 near the critical magnetic field of Hc ≅ 23.5 tesla. The giant H- and T-dependent suppression of κ can be explained by the combined result of resonant scattering of phononic heat carriers with magnetic energy levels and increased phonon scattering due to enhanced spin fluctuation at Hc, unequivocally revealing the existence of strong spin-phonon coupling. Moreover, we find an experimental indication that the remaining magnetic heat transport along the b-axis becomes almost gapless at the magnetic quantum critical point realized at Hc.

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“…In this material, the S = 1/2 magnetic moments of the Cu 2+ ions are arranged in a zigzag shaped ladder along the b-axis. The structure leads to frustrated interactions between the leg coupling (JLeg ~ 140 K) and the Next-nearest-neighbor coupling (JNNN ~ 140 K) [10]. Along the rung direction (c-axis), the Cu-O-Cu super-exchange interaction leads to the rung coupling (JRung ~ 3JLeg/4).…”

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