Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite

Akazawa, Masatoshi; Shimozawa, Masaaki; Kittaka, Shunichiro; Sakakibara, Toshiro; Okuma, Ryutaro; Hiroi, Zenji; Lee, Hyun Yong; Kawashima, Naoki; Han, Jung Hoon; Yamashita, Minoru

doi:10.1103/physrevx.10.041059

Cited by 32 publications

(23 citation statements)

References 61 publications

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“…Specifically, in 1D spin systems, the thermal conductivity is notably enhanced along the chains 24,25 . Spin contributions to thermal conductivity can be larger than lattice contributions in some frustrated magnets [26][27][28] . For pharmacosiderite, one expects a larger thermal conductivity along the c layer as magnon excitations are confined in the layer.…”

Section: Resultsmentioning

confidence: 99%

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

et al. 2021

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Dimensionality is a critical factor in determining the properties of solids and is an apparent built-in character of the crystal structure. However, it can be an emergent and tunable property in geometrically frustrated spin systems. Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet, pharmacosiderite, via muon spin resonance and neutron scattering. We find that the spin correlation exhibits a two-dimensional characteristic despite the isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe3+ ions in the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation by geometrical frustration based on spin wave calculations. Moreover, we suggest that even one-dimensionalisation occurs in the decoupled layers, generating low-energy and one-dimensional excitation modes, causing large spin fluctuation in the classical spin system. Pharmacosiderite facilitates studying the emergence of low-dimensionality and manipulating anisotropic responses arising from the dimensionality using an external magnetic field.

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Section: Resultsmentioning

confidence: 99%

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

et al. 2021

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“…The field of topology is not restricted to fermions, but also applies to bosons. The topological features of phonons [6][7][8][9][10][11][12], photons [13][14][15][16][17], and magnons [18][19][20][21][22][23][24][25], however, are more subtle due to the lack of the Pauli exclusion principle which results in quantized transport. In this Paper we focus on magnons, because they are easily manipulated by external magnetic fields.…”

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confidence: 99%

“…Previous reports addressed thermal Hall effects in collinear ferromagnets with Dzyaloshinskii-Moriya interaction (DMI) and dipolar interactions [18,19,, in weak ferromagnets with scalar spin chirality or due to magnetic fields [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73], in noncollinear antiferromagnets [74] or in paramagnets [12,41,44,59,[75][76][77][78][79][80]. Here, we present a thermal Hall effect in collinear antiferromagnets without DMI, which may even be present without external fields.…”

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Thermal Hall effect of magnons in collinear antiferromagnetic insulators: signatures of magnetic and topological phase transitions

Neumann,

Mook,

Henk

et al. 2021

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We demonstrate theoretically that the thermal Hall effect of magnons in collinear antiferromagnetic insulators is an indicator of magnetic and topological phase transitions in the magnon spectrum. The transversal heat current of magnons caused by a thermal gradient is calculated for an antiferromagnet on a honeycomb lattice. An applied magnetic field drives the system from the antiferromagnetic phase via a spin-flop phase into the field-polarized phase. Besides these magnetic phase transitions we find topological phase transitions within the spin-flop phase. Both types of transitions manifest themselves in prominent and distinguishing features in the thermal conductivities; depending on the temperature, the conductivity changes by several orders of magnitude, providing a tool to discern experimentally the two types of phase transitions. We include numerical results for the van der Waals magnet MnPS 3 .

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“…As these excitations are charge neutral, they do not respond to an electromagnetic field but can carry heat and potentially exhibit the thermal Hall effect [5,6] without resorting to the Lorentz force. Recently, finite thermal Hall conductivity κ xy has been experimentally resolved in several insulating magnets on geometrically frustrated lattices [7][8][9][10][11][12][13], which has been interpreted as the predicted topological thermal Hall effect of bosonic spin excitations. These topological excitations have gained great interest as they have the potential to realize dissipationless spintronic/magnonic devices [14].…”

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confidence: 99%

“…In addition, quantitative comparison of the observed thermal Hall effect with theory is difficult and often impossible in most frustrated quantum magnets, because their ground states and low-energy excitations are not fully understood. Furthermore, recent studies on the insulating magnets such as kagome antiferromagnets with weak lattice-spin coupling revealed the presence of non-negligible contribution of thermal Hall effect of phononic origin [13,[16][17][18] which makes it difficult to single out the topological part. In fact, the thermal Hall conductivity κ xy observed in frustrated pyrochlore ferromagnet Lu 2 V 2 O 7 , which contains a two-dimensional (2D) kagome lattice, is much larger than that expected from the DM interaction determined by the density functional theory [19,20], indicating that the observed κ xy may not be solely of the topological origin.…”

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Intrinsic suppression of topological thermal Hall effect in an exactly solvable quantum magnet

Suetsugu,

Yokoi,

Totsuka

et al. 2021

Preprint

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In contrast to electron (fermion) systems, topological phases of charge neutral bosons have been poorly understood despite recent extensive research on insulating magnets. The most important unresolved issue is how the inevitable inter-bosonic interactions influence the topological properties. It has been proposed that the quantum magnet SrCu2(BO3)2 with an exact ground state serves as an ideal platform for this investigation, as the system is expected to be a magnetic analogue of a Chern insulator with electrons replaced by bosonic magnetic excitations (triplons). Here, in order to examine topologically protected triplon chiral edge modes in SrCu2(BO3)2, we measured the thermal Hall conductivity κxy with extremely high accuracy. Contrary to the theoretical expectations, no discernible κxy was observed, which is at most ∼ 1/20 of the prediction if present. This implies that even relatively weak inter-particle interactions seriously influence the topological transport properties at finite temperatures. These demonstrate that, in contrast to fermionic cases, the picture of non-interacting topological quasi-particles cannot be naively applied to bosonic systems, calling special attention to the interpretation of the topological bosonic excitations reported for various insulating magnets.

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Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite

Cited by 32 publications

References 61 publications

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters

Thermal Hall effect of magnons in collinear antiferromagnetic insulators: signatures of magnetic and topological phase transitions

Intrinsic suppression of topological thermal Hall effect in an exactly solvable quantum magnet

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