Pascal Puphal

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Experimental control of ground states is a holy grail in physics, enabling the design of exotic
states as superconductivity, topological magnetism, quantum spin liquids (QSL) etc. There are
various ways to control materials: chemical pressure, chemical strain, chemical doping, entropy,
topochemistry, dimensionality/heterostructures, external pressure, external strain, optical
pumping etc. In my talk, I will discuss how pressure is already used in synthesis to control
systems and next show how far via chemical control combined with external stimuli we can shape
our desired materials. This will be discussed on all kinds of materials in the gold standard form of
materials: single crystals. The talk starts with the class of high TC superconductors with the new
family of nickelates,[1-4]. Here, the class of infinite layer nickelates, show a promising example of
material design, where the unique Ni1.2+ state is reached via topochemistry and optimal doping is
realized via epitaxial strain. We could show that superconductivity is bound to thin films [1-3], as
for bulk doping is reaching a solubility limit. Nickelates realize a second class, where we found a
unique stacking pattern [4], that allows for heterostructure like design and with the addition of
pressure as a tuning parameter TC of up to 80 K are reached [4]. Afterwards, focused on the
control parameters and their scope low dimensional quantum magnets [5], frustrated magnets,
where we can readily switch between a QSL and order [6] and topological magnets [7] will be
discussed.
[1] P. Puphal et al., APL Mater 11, 081107 (2023)
[2] P. Puphal et al., Phys. Rev. Materials 7, 014804 (2023).
[3] P. Puphal et al., Sci. Adv. 7, eabl8091 (2021)
[4] P. Puphal et al,. arXiv:2312.07341 (2023).
[5] P. Puphal et al., PRB 93, 174121 (2016)
[6] D. Chatterjee, P. Puphal et al., PRB 107, 125156 (2023).
[7] P. Puphal et al., PRB 101, 214416 (2020)

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MPI für Festkörperforschung Stuttgart
Seminar Room of the Institute of Physics II
Contact: Erwann/Matteo