Physical Review Letters

Direct observation of the nonaxisymmetric vortex in superfluid B3

Yasushi Kondo, J. S. Korhonen, M. Krusius, Vladimir V. Dmitriev, Yury Mukharsky, Edouard B Sonin, Григорий Ефимович Воловик

Published Jul 1, 1991• 152 citations

Publisher

Abstract

We present experimental proof that in rotating $^{3}\mathit{B}$ the vortex-core transition temperature ${\mathit{T}}_{\mathit{V}}$ separates axisymmetric vortices above ${\mathit{T}}_{\mathit{V}}$ from vortices with spontaneously broken axial symmetry below ${\mathit{T}}_{\mathit{V}}$. The nonaxisymmetry is observed in the presence of coherent spin precession as a new soft Goldstone mode, manifested as oscillations and spiral twisting of the core anisotropy axis. These are driven by the precessing spin via spin-orbit coupling and lead to magnetic relaxation from viscous losses, which depend on vortex pinning.

DOI: 10.1103/physrevlett.67.81

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Physical Review Letters

Direct observation of the nonaxisymmetric vortex in superfluid B3

Yasushi Kondo, J. S. Korhonen, M. Krusius, Vladimir V. Dmitriev, Yury Mukharsky, Edouard B Sonin, Григорий Ефимович Воловик

Published Jul 1, 1991• 152 citations

Publisher

Abstract

We present experimental proof that in rotating

^{3}\mathit{B}

the vortex-core transition temperature

{\mathit{T}}_{\mathit{V}}

separates axisymmetric vortices above

{\mathit{T}}_{\mathit{V}}

from vortices with spontaneously broken axial symmetry below

{\mathit{T}}_{\mathit{V}}

. The nonaxisymmetry is observed in the presence of coherent spin precession as a new soft Goldstone mode, manifested as oscillations and spiral twisting of the core anisotropy axis. These are driven by the precessing spin via spin-orbit coupling and lead to magnetic relaxation from viscous losses, which depend on vortex pinning.

DOI: 10.1103/physrevlett.67.81

Related papers

Vortices with spontaneously broken axisymmetry in B3

M.M. Salomaa, Григорий Ефимович Воловик

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Pressure dependence of axisymmetric vortices in superfluid B3

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The pressure dependence of the vortex core in rotating $^{3}\mathit{B}$ is studied in the Ginzburg-Landau formalism with two distinct models of the strong-coupling corrections. The parametrization of Sauls and Serene [Phys. Rev. B 24, 183 (1981)] predicts a transition from a core with large magnetic moment below \ensuremath{\sim}10 bars to one with small magnetic moment for higher pressures, in qualitative agreement with experiments. The earlier one-parameter model of Brinkman, Serene, and Anderson predicts no such transition, with the core having a large moment for all values of the parameter \ensuremath{\delta}.The pressure dependence of the vortex core in rotating $^{3}\mathit{B}$ is studied in the Ginzburg-Landau formalism with two distinct models of the strong-coupling corrections. The parametrization of Sauls and Serene [Phys. Rev. B 24, 183 (1981)] predicts a transition from a core with large magnetic moment below \ensuremath{\sim}10 bars to one with small magnetic moment for higher pressures, in qualitative agreement with experiments. The earlier one-parameter model of Brinkman, Serene, and Anderson predicts no such transition, with the core having a large moment for all values of the parameter \ensuremath{\delta}.

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N. L. Smith, W H Heathcote, J. M. Krueger +1 more

We have measured the precession frequency of a vortex lattice in a Bose-Einstein condensate of Rb87 atoms. The observed mode corresponds to a collective motion in which all the vortices in the array are tilted by a small angle with respect to the z axis (the symmetry axis of the trapping potential) and synchronously rotate about this axis. This motion corresponds to excitation of a Kelvin wave along the core of each vortex and we have verified that it has the handedness expected for such helical waves, i.e., precession in the opposite sense to the rotational flow around the vortices.We have measured the precession frequency of a vortex lattice in a Bose-Einstein condensate of Rb87 atoms. The observed mode corresponds to a collective motion in which all the vortices in the array are tilted by a small angle with respect to the z axis (the symmetry axis of the trapping potential) and synchronously rotate about this axis. This motion corresponds to excitation of a Kelvin wave along the core of each vortex and we have verified that it has the handedness expected for such helical waves, i.e., precession in the opposite sense to the rotational flow around the vortices.

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Collective motion of quantized vortex lines in rotating superfluid B3

M. Krusius, J. S. Korhonen, Y. Kondo +1 more

Insight in the dynamics of quantized vortex lines has been obtained by performing NMR measurements in uniformly rotating superfluid $^{3}\mathit{B}$ . Compared to superfluid $^{4}\mathrm{He}$ , in $^{3}\mathit{B}$ the viscosity of the normal component is three orders of magnitude larger and the pinning of vortices is weaker. The collective modes governing the hydrodynamic response of an array of vortex lines are highly overdamped. Two distinct modes are identified: (1) a relatively fast mutual-friction-resisted mode, which controls the redistribution of the vortex density on a time scale of a few seconds, and (2) an exponentially relaxing slow mode with a time constant of a few minutes, which governs asymptotically the approach to equilibrium at nearly constant vortex density. Measurement of the fast motion allows us to extract the dissipative mutual friction. The slow mode is dominated by the elastic tension along the vortex line and by weak pinning at the top and bottom surfaces of the rotating container. With increasing vortex density the surface pinning becomes a collective process, in which coherently moving groups of vortices are pinned in unison. Collective pinning is a result of the shear elasticity related to the crystalline order of the vortex lattice. Our measurements on the slow mode indicate that the crystalline correlation extends over many lattice spacings.Insight in the dynamics of quantized vortex lines has been obtained by performing NMR measurements in uniformly rotating superfluid $^{3}\mathit{B}$. Compared to superfluid $^{4}\mathrm{He}$, in $^{3}\mathit{B}$ the viscosity of the normal component is three orders of magnitude larger and the pinning of vortices is weaker. The collective modes governing the hydrodynamic response of an array of vortex lines are highly overdamped. Two distinct modes are identified: (1) a relatively fast mutual-friction-resisted mode, which controls the redistribution of the vortex density on a time scale of a few seconds, and (2) an exponentially relaxing slow mode with a time constant of a few minutes, which governs asymptotically the approach to equilibrium at nearly constant vortex density. Measurement of the fast motion allows us to extract the dissipative mutual friction. The slow mode is dominated by the elastic tension along the vortex line and by weak pinning at the top and bottom surfaces of the rotating container. With increasing vortex density the surface pinning becomes a collective process, in which coherently moving groups of vortices are pinned in unison. Collective pinning is a result of the shear elasticity related to the crystalline order of the vortex lattice. Our measurements on the slow mode indicate that the crystalline correlation extends over many lattice spacings.

Physical review. B, Condensed matterJun 1, 199380 citations

We present experimental proof that in rotating

^{3}\mathit{B}

the vortex-core transition temperature

{\mathit{T}}_{\mathit{V}}

separates axisymmetric vortices above

{\mathit{T}}_{\mathit{V}}

from vortices with spontaneously broken axial symmetry below

{\mathit{T}}_{\mathit{V}}

This paper reports the discovery of a new breaking of symmetry of the quantized vortex lines in superfluid

^{3}\mathit{B}

: Vortices with broken axisymmetry are found energetically more favorable than any of the axisymmetric ones in the weak-coupling limit. Based on our extensive numerical minimization of the vortex free-energy functional, we identify the vortices occurring in rotating

^{3}\mathit{B}

at low pressures as v vortices having---in addition to broken space parity P---also broken axisymmetry Q with the nonaxisymmetry quantum number \ensuremath{\Vert}Q\ensuremath{\Vert}=2, and with superfluid core in the axiplanar state.

A numerical solution of the Ginzburg-Landau equations for superfluid

^{3}\mathit{B}

vortices gives the following results: The low-pressure vortex is a new ``double core vortex'' whose rotational symmetry around the vortex axis is broken. The high-pressure vortex is the v vortex. The theory gives a transition between these vortices which is in excellent agreement with experiments.

The pressure dependence of the vortex core in rotating

^{3}\mathit{B}

is studied in the Ginzburg-Landau formalism with two distinct models of the strong-coupling corrections. The parametrization of Sauls and Serene [Phys. Rev. B 24, 183 (1981)] predicts a transition from a core with large magnetic moment below \ensuremath{\sim}10 bars to one with small magnetic moment for higher pressures, in qualitative agreement with experiments. The earlier one-parameter model of Brinkman, Serene, and Anderson predicts no such transition, with the core having a large moment for all values of the parameter \ensuremath{\delta}.

Insight in the dynamics of quantized vortex lines has been obtained by performing NMR measurements in uniformly rotating superfluid

^{3}\mathit{B}

. Compared to superfluid

^{4}\mathrm{He}

, in

^{3}\mathit{B}

the viscosity of the normal component is three orders of magnitude larger and the pinning of vortices is weaker. The collective modes governing the hydrodynamic response of an array of vortex lines are highly overdamped. Two distinct modes are identified: (1) a relatively fast mutual-friction-resisted mode, which controls the redistribution of the vortex density on a time scale of a few seconds, and (2) an exponentially relaxing slow mode with a time constant of a few minutes, which governs asymptotically the approach to equilibrium at nearly constant vortex density. Measurement of the fast motion allows us to extract the dissipative mutual friction. The slow mode is dominated by the elastic tension along the vortex line and by weak pinning at the top and bottom surfaces of the rotating container. With increasing vortex density the surface pinning becomes a collective process, in which coherently moving groups of vortices are pinned in unison. Collective pinning is a result of the shear elasticity related to the crystalline order of the vortex lattice. Our measurements on the slow mode indicate that the crystalline correlation extends over many lattice spacings.