Collaborative Research Center 360
Constrained Quantum Matter
Less is more!
We use carefully chosen constraints to design and
manipulate quantum states in solids, seeking to create new quantum
materials and explore conceptual challenges from quantum information
theory to non-equilibrium physics.
Our outreach project in Augsburg is looking for a motivated student for a Hiwi position!
Our annual Retreat Meeting is coming up!
Frank Pollmann awarded with the Gottfried Wilhelm Leibniz prize 2026
In 2026, another member of the TRR360, Frank Pollmann from the Technical University Munich, is awarded with the Gottfried Wilhelm Leibniz prize 2026 which is handed out by the German Research Foundation (DFG). He will be given this prestigious prize in March 2026 for his work on statistical mechanics of many-body systems and their link to quantum information theory. More details can be found here.
2025 James C. McGroddy Prize awarded to Hidenori Takagi
We are very proud to announce that one member of the TRR 360, Hidenori Tagaki from the MPI for solid-state research in Stuttgart, will be awarded with the 2025 James C. McGroody Prize for New Materials. He is honoured “for seminal theoretical and experimental research, materials design and discoveries that pioneered the exploration of novel forms of topological quantum matter in spin-orbit assisted Mott insulators realized in transition metal oxides”. More information can be found here. The prize will be presented in March 2025.
Next events
Recent Articles
Chatterjee, S.; Agarwal, A.; Borkenhagen, R.; Kuntscher, C. A.; Winiarski, M. J.; Pavlosiuk, O.; Wiśniewski, P.; Kaczorowski, D. Anisotropic magnetotransport and optical response of the multiband low-carrier antiferromagnet DyPtSb Journal Article Phys. Rev. B 114, 154412 (2026). @article{chatterjeeAnisotropicMagnetotransportOptical2026,We report a combined study of the magnetic, electrical transport, optical reflectivity, and electronic properties of single-crystalline DyPtSb, a half-Heusler antiferromagnet that orders at 2.2 K. The electrical resistivity exhibits semiconductor-like behavior and the Hall response becomes strongly nonlinear at low temperatures, indicating multiband transport with hole- and electron-type pockets. Angular magnetoresistance measurements revealed occurrence of twofold and fourfold symmetry components, both of which change sign near magnetic field of 4 T at 2 K, suggesting a field-induced modification of the electronic structure near the crossover from the antiferromagnetic to the spin-polarized regime. The optical spectroscopy revealed a temperature-dependent plasma edge and a Drude response, consistent with the bulk electrical transport data. In contrast to the characteristic feature of three-dimensional Dirac and Weyl semimetals, the optical conductivity of DyPtSb does not exhibit clear linear-in-frequency behavior at low energy. The results of ab initio electronic band-structure calculations revealed that the compound is a narrow-gap semiconductor, showing pronounced anisotropy of valence bands and strong sensitivity to magnetic polarization. DyPtSb was characterized as a multiband low-carrier antiferromagnet whose electrical transport properties are closely tied to the evolution of its electronic structure. |
Jarc, G.; Tartaglia, G.; Gabriele, F.; Forte, F.; Guarino, A.; Montanaro, A.; Rigoni, E. M.; Khatiwada, N.; Lincetto, C.; Bartolini, G.; Mastropasqua, A.; Mathengattil, S. Y.; Malvestuto, M.; Waqee-Ur-Rehman, M.; Fittipaldi, R.; Deisenhofer, J.; Tsirlin, A. A.; Vecchione, A.; Cuoco, M.; Fausti, D. Raman signatures of a non-reciprocal magnetic phase transition in Ca2RuO4 Unpublished (2026), arXiv.2609.07565. @unpublished{jarc2026ramansignaturesnonreciprocalmagnetic,The magnetic behavior of Ca2RuO4 represents a unique puzzle due to the interplay of strong electronic correlations, magneto-elastic interactions, and large spin-orbit coupling. At low temperatures, an anomalous Mott insulating state emerges, characterized by a complex antiferromagnetic order with a collective amplitude excitation of the magnetic moment which has been discussed in analogy with the Higgs mode. We report here evidence of a magnetic first-order phase transition driven by an out-of-plane magnetic field along the crystallographic c-axis of Ca2RuO4. Raman measurements in magnetic field reveal the emergence of mode of magnetic origin and a concomitant modification of the coupling between a phonon and the Higgs amplitude mode. Both the Raman features are characterized by a non-reciprocal hysteresis in magnetic field. Surprisingly, the observed phase transition does not affect the Raman scattering from the in-plane magnons, indicating that the dipolar antiferromagnetic order is preserved. This is consistent with the onset of a new quadrupolar field-controlled state, whose fluctuations structure can trigger an hybridization between the lattice and the magnetic Higgs mode resulting in the observed Raman features. |
Zhang, Y. -S.; Isobe, M.; Takagi, H.; Huang, D. Electronic tuning of the soft-phonon transport anomaly in Ta2Ni(SxSe1-x)5 Journal Article Phys. Rev. Lett. 137, 106503 (2026). @article{l5xq-2yrt,Ta2NiSe5 continues to be investigated for its phase transition at 𝑇c=326 K, where it develops both an electronic gap and a distortion of its Ta/Ni chains. One intriguing feature at 𝑇c seen in thermal transport is the giant anisotropic scattering of phonons moving perpendicular to the chains, which is apparently associated with the softening of a transverse acoustic phonon, but whose microscopic origin and significance demand clarification. By tuning the normal-state band overlap or gap with S substitution, we uncover a close connection between this soft-phonon transport anomaly and underlying electronic instabilities: when Ta2Ni(S𝑥Se1−𝑥)5 approaches a band insulator at high 𝑥, and signatures of the electronic transition are suppressed, the soft-phonon transport anomaly concomitantly vanishes. Our results establish the following picture for the Ta2Ni(S𝑥Se1−𝑥)5 family: near the S end, a sole lattice instability gives rise to a weak structural transition with 𝑇c approaching 130 K. Near the Se end, additional electronic instabilities boost 𝑇c up to 326 K and amplify experimental signatures of the transition. The strong interaction between electrons, holes, and the lattice is manifested as a soft-phonon transport anomaly accompanied by electronic fluctuations, which include excitonic and hybridization-gap fluctuations. |
Schilberth, F.; Vasin, K.; Knauft, M.; Kondákor, M.; Vuckovic, M.; Herrmann, N.; Penc, K.; Minola, M.; Keimer, B.; Martinez, V. A.; Panda, K.; Sirenko, A. A.; Prodan, L.; Tsurkan, V.; Tsirlin, A. A.; Kézsmárki, I.; Deisenhofer, J. (2026), arXiv:2608.01062. @unpublished{schilberth_magnetic_2026, |
Gippius, A. A.; Zhurenko, S. V.; Tkachev, A. V.; Gunbin, A. V.; Büttgen, N.; Schaedler, M.; Silkin, I. G.; Morozov, I. V.; Bogach, A. V.; Sobolev, A. V.; Presniakov, I. A.; Moskvin, A. S. Short-range helical magnetic order in FeP1-xAsx (x = 0.33 and 0.5) Journal Article J. Magn. Magn. Mater. 651, 174177 (2026). @article{GIPPIUS2026174177,Although the FeP1-xAsx solid solution compounds are isostructural with the binary helimagnets FeP and FeAs with MnP-type structure (sp. gr. Pnma) of the B31 family, their magnetic structure remained unclear. We studied two members of this family (x = 0.33 and 0.5) via microscopic site-selective techniques such as Mössbauer and NMR spectroscopy. Our results indicate that the helimagnetic nature of the ground state is preserved, but undergoes significant modifications. In particular, its ordering range seems to become drastically shorter, so that the local fields on the non-magnetic phosphorus atoms decrease several times compared to those in FeP, and even local fields on iron slightly decrease compared to FeP and FeAs. The ordering temperature for these fragmented structures is suppressed down to 20–30 K, which is significantly lower than the TN values for FeP and FeAs. Additionally, both compounds demonstrate higher sustainability to the external field than the parent compound FeP. |
Impressions from past events








































The research programme
We seek to design and utilize new quantum states by taking advantage of the recently developed capability to tailor electron systems in complex materials through a variety of complementary constraints, focusing on spin-momentum locking, gauge structures of interacting spin systems, and kinetic constraints.
News
Here you can find all the important news around the project ConQuMat: recent publication, internal events for project members and opening for various positions.
Outreach - Öffentlichkeitsarbeit
Dive with us into the fascinating world of quantum matter! (science communication offers in German)
Es gibt viele Angebote, um die Forschung aus dem Projekt ConQuMat der Öffentlichkeit zugänglich zu machen. Egal ob durch einen Blog, Spiele oder Erlebnisveranstaltungen – tauchen Sie mit uns in die faszinierende Welt der Quantenmaterie ein!