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@PHDTHESIS{Kuespert:642367,
      author       = {Kuespert, Julia},
      othercontributors = {Chang, Johan and Moser, Simon and Janoschek, Marc},
      title        = {{C}ompeting {S}tates in the {U}nconventional
                      {S}uperconductor {L}a$_{2-x}${S}r$_x${C}u{O}$_4$},
      school       = {University of Zurich},
      type         = {Dissertation},
      publisher    = {University of Zurich},
      reportid     = {PUBDB-2025-05522},
      pages        = {127},
      year         = {2024},
      note         = {Dissertation, University of Zurich, 2024},
      abstract     = {In strongly correlated systems, phases and states are often
                      highly intertwined. New insights can be gained by
                      influencing the interplay of the phenomena, for example, by
                      temperature, magnetic field, or strain. Benefiting from all
                      three tuning knobs, we contributed to the research on the
                      intriguing phase diagram of (La-based) cuprates. The
                      experiments were mostly carried out at x-ray diffraction and
                      angle-resolved photoemission endstations of state-of-the-art
                      synchrotrons. The first pair of interacting states examined
                      was the superconducting gap and the pseudogap. In a
                      high-resolution angle-resolved photoemission spectroscopy
                      study, we extract the evolution of the antinodal gap as a
                      function of temperature. The gap increases below the
                      pseudogap onset. From the linear decrease with temperature
                      below the superconducting transition at we deduce, that the
                      two orders are competing. Lowering the temperature,
                      integrated spectral weight reduces in the pseudogap state,
                      but starts to regain already before the onset of
                      superconductivity. Thus, superconductivity and the pseudogap
                      interact with a third energy scale, possibly linked to
                      charge order. Charge order upon application of compressive
                      pressure in LaSrCuO (LSCO) was investigated by diffraction
                      for the greater part of the here presented work. Stripe
                      order in LSCO manifests in the and planes, where are the
                      Miller indices. If pressure is applied along the Cu-O
                      direction, stripe order peaks enhance by a factor of two in
                      the direction perpendicular to the strain. They are
                      suppressed to the background in the direction along the
                      strain. Uniaxial pressure along the Cu-O direction lifts the
                      domain degeneracy of both spin and charge order domains.
                      This on one hand determines the fundamental symmetry of
                      charge and spin order to be uniaxial stripes instead of a
                      checkerboard structure. On the other hand, it confirms that
                      the two orders in LSCO are strongly intertwined. By
                      comparing experimentally measured and simulated diffraction
                      patterns, we showed, that the space group of LSCO in the
                      charge ordered state is not orthorhombic as the average
                      crystal structure, but monoclinic. In another hard x-ray
                      diffraction study, we applied pressure along the -axis of
                      LSCO . Within the superconducting phase, the charge order
                      amplitude raises with strain, while it is not affected in
                      the normal state. Adding a magnetic field along the -axis to
                      the system, we initially, without pressure, reproduce the
                      well-known augmentation of charge order below as
                      superconductivity is weakened. Charge order in LSCO with
                      strain along the -axis and fields up to 10,T is still
                      boosted within the superconducting phase. However, the
                      increase is lower than if there was solely the magnetic
                      field. The magnetic field does not have an effect in the
                      normal state. Our observations point towards uniaxial -axis
                      strain in LSCO coupling directly to the competing
                      interaction of superconductivity and charge order.},
      cin          = {DOOR ; HAS-User},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {6G3 - PETRA III (DESY) (POF4-6G3)},
      pid          = {G:(DE-HGF)POF4-6G3},
      experiment   = {EXP:(DE-H253)P-P21.1-20150101 /
                      EXP:(DE-H253)D-BW5-20150101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.5167/UZH-267112},
      url          = {https://bib-pubdb1.desy.de/record/642367},
}