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Direct Measurement of the Soft Mode Driving a Quantum Phase Transition

Libersky, M. and McKenzie, R. D. and Silevitch, D. M. and Stamp, P. C. E. and Rosenbaum, T. F. (2021) Direct Measurement of the Soft Mode Driving a Quantum Phase Transition. . (Unpublished)

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Quantum phase transitions in spin systems are supposed to be accompanied by a soft collective mode, which has not been seen in experiments. Here, we directly measure the low energy excitation modes of a well-known realization of the Ising model in transverse field, LiHoF₄, using microwave spectroscopy techniques to probe energies well below what is accessible via neutron scattering experiments. Instead of the single excitation expected for a simple quantum Ising system, we find and characterize a remarkable array of 'electronuclear' modes, arising from coupling of the spin-1/2 Ising electronic spins to a bath of spin-7/2 Ho nuclear spins. The lowest-lying electronuclear mode softens at the approach to the quantum critical point from below and above, a softening that can be quenched with the application of a longitudinal magnetic field. The electronuclear mode structure has direct implications for the Ising systems that serve as the building blocks of adiabatic quantum computers and quantum annealers.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Silevitch, D. M.0000-0002-6347-3513
Additional Information:Attribution 4.0 International (CC BY 4.0). The experimental work at Caltech was supported by US Department of Energy Basic Energy Sciences Award DE-SC0014866. P.C.E.S. acknowledges support at Caltech from Simons Foundation Award 568762 and National Science Foundation Award PHY-1733907. The theoretical work at UBC was supported by the National Sciences and Engineering Research Council of Canada.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0014866
Simons Foundation568762
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Record Number:CaltechAUTHORS:20210202-095237849
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107858
Deposited By: George Porter
Deposited On:03 Feb 2021 21:32
Last Modified:03 Feb 2021 21:32

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