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@INPROCEEDINGS{Heinze:1044579,
      author       = {Heinze, Leonie},
      title        = {{Q}uantum criticality and dimensional reduction of a
                      sawtooth chain material: a case study},
      reportid     = {FZJ-2025-03259},
      year         = {2025},
      abstract     = {Quantum magnets with geometrical frustration stand out due
                      to their highly degenerate ground states and their
                      susceptibility to be tuned regarding their effective
                      dimensionality by applying pressure or magnetic field [1].
                      Such tuning can lead to quantum phase transitions from
                      ordered to disordered states, or vice versa, with the
                      emergent quantum critical points (QCPs) determining the
                      deformed entropy landscapes in the respective phase
                      diagrams. While, in general, there is a fundamental interest
                      in using the properties arising from such distorted entropy
                      landscapes for applications (e.g. the magnetocaloric effect
                      for low-temperature cooling [2,3]), I address here the role
                      of residual exchange interactions in real materials. I
                      demonstrate that a QCP can develop on a lower effective
                      energy scale measured against the leading exchange couplings
                      in the system.In this talk, I present a case study on the
                      mineral atacamite Cu$_2$Cl(OH)$_3$, a sawtooth-chain
                      compound where the chain units [J ~ 336 K (basal-basal),
                      J’ ~ 102 K (basal-apical)] are embedded into a weak
                      three-dimensional network of interchain couplings [4]. I
                      will show that the magnetic phase diagram of atacamite
                      contains a field-induced quantum critical point at 21.9(1) T
                      (H || c axis) which emerges on a much lower energy scale
                      compared to the leading terms in the spin Hamiltonian
                      derived by means of density-functional theory [4,5].
                      Further, the QCP separates field regions with and without
                      long-range magnetic order. In the latter, underpinned by
                      numerical results, the sawtooth chains decompose into two
                      independent subunits, but far away from full field
                      polarization of the material [5].},
      month         = {Mar},
      date          = {2025-03-16},
      organization  = {APS Global Physics Summit, Anaheim
                       (USA), 16 Mar 2025 - 21 Mar 2025},
      subtyp        = {Invited},
      cin          = {JCNS-4 / JCNS-3 / MLZ / JCNS-FRM-II},
      cid          = {I:(DE-Juel1)JCNS-4-20201012 / I:(DE-Juel1)JCNS-3-20170926 /
                      I:(DE-588b)4597118-3 / I:(DE-Juel1)JCNS-FRM-II-20110218},
      pnm          = {6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ)
                      (POF4-6G4) / 632 - Materials – Quantum, Complex and
                      Functional Materials (POF4-632)},
      pid          = {G:(DE-HGF)POF4-6G4 / G:(DE-HGF)POF4-632},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/1044579},
}