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Probing many-body localization in a disordered quantum magnet

Silevitch, D. M. and Aeppli, G. and Rosenbaum, T. F. (2018) Probing many-body localization in a disordered quantum magnet. . (Submitted)

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Excitations in disordered systems are typically categorized as localized or delocalized, depending on whether they entail disturbances extending throughout the system or are confined to small, generally nanometer scale, subsystems. Such categorization is impossible to achieve using traditional spectroscopy where the response to a weak oscillating (ac) electromagnetic probe is measured as a function of frequency. However, the localized excitations can be separated from each other as well as the delocalized continuum by measuring a spectral "hole" in the ordinary response while a large amplitude pump is imposed at a fixed frequency. Localized excitations will result in a very sharp "hole," and any residual couplings to other excitations, both localized and extended, will determine its detailed shape. This technique probes incoherent lifetime effects as well as coherent mixing or quantum interference phenomena, describable in terms of the Fano effect. Here we show that in a disordered Ising magnet, LiHo0.045Y0.955F4, the quality factor Q for spectral holes, the ratio of the drive frequency to their width, can be as high as 100,000. In addition, we can tune the dynamics of the quantum degrees of freedom by sweeping the quantum mixing parameter through zero via the amplitude of the ac pump as well as a static external transverse field. The zero-crossing is associated with a dissipationless response at the drive frequency. The identification of such a point where localized degrees of freedom are minimally mixed with their environment in a dense and disordered dipolar coupled spin system implies control over the bath coupling of qubits emerging from strongly interacting many-body systems.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Silevitch, D. M.0000-0002-6347-3513
Additional Information:(Submitted on 16 Jul 2017 (v1), last revised 18 Jan 2018 (this version, v2) We thank G. Refael and Markus Müller for helpful discussions. The work at Caltech was supported by US Department of Energy Basic Energy Sciences Award de-sc0014866.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0014866
Record Number:CaltechAUTHORS:20180205-091437437
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84668
Deposited By: Ruth Sustaita
Deposited On:05 Feb 2018 21:11
Last Modified:09 Mar 2020 13:19

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