Pion Condensation by Rotation in a Magnetic Field

Liu, Yizhuang; Zahed, Ismaïl

doi:10.1103/physrevlett.120.032001

Cited by 59 publications

(71 citation statements)

References 37 publications

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“…Returning to α-RuCl 3 , small Heisenberg interactions, J, are also a sought-after feature of candidate Kitaev materials. When these dominant magnetic effects are suppressed, the remaining terms in the anisotropic spin Hamiltonian are thought to give rise to fractional spin excitations (of Majorana [15,18,42] or generalized Majorana character [43]) and to spin-liquid ground states in the presence of an applied magnetic field [9,16,44]. It is clear [9] that the thermal conductivity measured in α-RuCl 3 shows strong spin-phonon scattering effects over the entire range of temperatures, but a detailed interpretation lies beyond the scope of a DC approach [20] and a theoretical analysis of phonon scattering by fractionalized spins is still awaited.…”

Section: Discussionmentioning

confidence: 99%

Giant thermal magnetoconductivity inCrCl3and a general model for spin-phonon scattering

Pocs

Leahy

Zheng

et al. 2020

Phys. Rev. Research

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Insulating quantum magnets lie at the forefront both of fundamental research into quantum matter and of technological exploitation in the increasingly applied field of spintronics. In this context, the magnetic thermal transport is a particularly sensitive probe of the elementary spin and exotic topological excitations in unconventional magnetic materials. However, magnetic contributions to heat conduction are invariably intertwined with lattice (phonon) contributions, and thus the issue of spin-phonon coupling in determining the spin and thermal transport properties of magnetic insulators becomes more important with every emergent topological magnetic system. Here we report the observation of an anomalously strong enhancement of the thermal conductivity, occurring at all relevant temperatures, in the layered honeycomb material CrCl3 in the presence of an applied magnetic field. Away from the magnetically ordered phase at low temperatures and small fields, there is no coherent spin contribution to the thermal conductivity, and hence the effect must be caused by a strong suppression of the phonon thermal conductivity due to magnetic fluctations, which are in turn suppressed by the field. We build an empirical model for the thermal conductivity of CrCl3 within a formalism assuming an independently determined number of spin-flip processes and an efficiency of the phonon scattering events they mediate. By extracting the intrinsic phonon thermal conductivity we obtain a quantitative description of our measured data at all fields and temperatures, and we demonstrate that the scattering efficiency is entirely independent of the applied field. In this way we use CrCl3 as a model system to understand the interactions between spin and phonon excitations in the context of thermal transport. We anticipate that the completely general framework we introduce will have broad implications for the interpretation of transport phenomena in magnetic quantum materials.

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Section: Discussionmentioning

confidence: 99%

Giant thermal magnetoconductivity inCrCl3and a general model for spin-phonon scattering

Pocs

Leahy

Zheng

et al. 2020

Phys. Rev. Research

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“…As a result, the degeneracy of each LL is lifted. The mechanism of π AE splitting by a rotation can cause π þ pion condensation [20]. We now explore this condensation in the vacuum and also matter for different overall charge constraints.…”

Section: Energy Densities Of a Bec Of Chiral Pionsmentioning

confidence: 99%

“…The condensation of charged pions by rotation in a magnetic field is for bosons, what the accumulation of vector charge in a vortex threaded by a magnetic field is for fermions [5], and in general in any rotating frame with a magnetic field [5][6][7]20]. For Dirac fermions this phenomenon is related to spectral flow and therefore to anomalies [5,20], of which the charged pionic condensate is its lowenergy manifestation in the QCD vacuum.…”

Section: Open Volumementioning

confidence: 99%

“…For Dirac fermions this phenomenon is related to spectral flow and therefore to anomalies [5,20], of which the charged pionic condensate is its lowenergy manifestation in the QCD vacuum. In both cases, the charge accumulation in the finite volume V ¼ LS is compensated by a deficiency of opposite charge outside of the volume V. Overall charge conservation is maintained by allowing the charge to move in or out of V as also suggested in Ref.…”

Section: Open Volumementioning

confidence: 99%

“…If the volume V ¼ SL is closed with no charge allowed to flow in or out, then charge conservation is to be enforced strictly in V [20]. Let μ be the charged chemical potential in the comoving frame.…”

Section: Closed Volumementioning

confidence: 99%

See 2 more Smart Citations

Rotating Dirac fermions in a magnetic field in 1+2 and 1+3 dimensions

Liu

Zahed

2018

Phys. Rev. D

Self Cite

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We consider the effects of an external magnetic field on rotating fermions in 1 þ 2 and 1 þ 3 dimensions. The dual effect of a rotation parallel to the magnetic field causes a net increase in the fermionic density by centrifugation, which follows from the sinking of the particle lowest Landau level in the Dirac sea for free Dirac fermions. In 1 þ d ¼ 2n dimensions, this effect is related to the chiral magnetic effect in 2n − 2 dimensions. This phenomenon is discussed specifically for both weak and strong interfermion interactions in 1 þ 2 dimensions. For QCD in 1 þ 3 dimensions with Dirac quarks, we show that in the strongly coupled phase with spontaneously broken chiral symmetry, this mechanism reveals itself in the form of an induced pion condensation by centrifugation. We use this observation to show that this effect causes a shift in the chiral condensate at leading order in the pion interaction, and to discuss the possibility for the formation of a novel pion superfluid phase in off-central heavy-ion collisions at collider energies.

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