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SUMMARY:Role of Many-Body Quantum Effects in μSR Measurements
DTSTART;VALUE=DATE-TIME:20220829T084000Z
DTEND;VALUE=DATE-TIME:20220829T090000Z
DTSTAMP;VALUE=DATE-TIME:20220826T105632Z
UID:indico-contribution-3658@indico.stfc.ac.uk
DESCRIPTION:Speakers: Matjaž Gomilšek (Jožef Stefan Institute\, Jamova 
 c. 39\, SI-1000 Ljubljana\, Slovenia)\nFor unambiguous interpretation of e
 xperimental µSR data\, a thorough understanding of quantum zero-point mot
 ion (ZPM) of muons in materials is essential. Namely\, while ZPM of light 
 nuclei like hydrogen and lithium is known to play a pivotal role in the st
 ructure and dynamics of many important classes of materials$^{1\,2}$\, qua
 ntum effects of muons in solids can be even stronger due to the lower mass
  of muons (~1/9 the mass of a proton) and can qualitatively change the mea
 sured µSR signal$^{3\,4}$.\n\nThere has been much interest in using *ab i
 nitio* computation of muon stopping sites in materials to aid in the inter
 pretation of µSR measurements. However\, most computational techniques em
 ployed have either neglected quantum muon ZPM\, or applied poorly controll
 ed approximations to it with little clarity around the limits of their app
 licability. To address this\, we have developed a unified description of l
 ight-particle ZPM in materials$^{4}$\, clarifying the roles many-body quan
 tum entanglement and anharmonicity play in determining the true ZPM regime
 . As proof of concept we applied these insights to our precision µSR quad
 rupolar level-crossing measurements on solid nitrogen\, α–N$_2$\, where
  they allowed us to significantly improve the accuracy of the extracted $^
 {14}$N nuclear quadrupolar coupling constant. This represents the first im
 provement in its accuracy in over 45 years\, despite the ubiquity of solid
  nitrogen in nature\, and a validation of our unified description of light
 -particle ZPM.\n\n$^{1}$T. E. Markland and M. Ceriotti\, Nat. Rev. Chem. *
 *2**\, 0109 (2018). $^{2}$E. Snider *et al.*\, Nature **586**\, 373 (2020)
 . $^{3}$S. J. Blundell\, R. De Renzi\, T. Lancaster and F. L. Pratt\, Muon
  Spectroscopy: An Introduction (Oxford University Press\, Oxford\, 2021). 
 $^{4}$M. Gomilšek *et al.*\, arXiv:2202.05859.\n\n![Quadrupolar level cro
 ssing resonance spectra of quantum muons in solid nitrogen.][1]\n\n  [1]: 
 http://quantum.ijs.si/wp-content/uploads/2022/07/Time-tracks-plot-2i4-adde
 d-JEMS-2022-figure-Time-frequency-dependence-Log-scale-For-JEMS-2022-Resiz
 e-300px-Resave-100.jpg\n\nhttps://indico.stfc.ac.uk/event/53/contributions
 /3658/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3658/
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