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| YbRh2Si2 | |
|---|---|
| Name | YbRh2Si2 |
| Formula | YbRh₂Si₂ |
| Appearance | crystalline |
| Crystal system | tetragonal |
| Space group | I4/mmm |
YbRh2Si2 is an intermetallic compound of ytterbium, rhodium, and silicon notable for its role as a model heavy fermion and quantum critical material. Discovered and developed in experimental programs centered on low-temperature condensed matter physics, it attracted attention through measurements that connect concepts from Kondo effect, Rudolf Mössbauer-era spectroscopy, and modern studies of quantum phase transitions performed at institutions such as the Max Planck Society and University of Cologne. The compound provides a platform linking techniques used by groups at facilities like the European Synchrotron Radiation Facility and the Institut Laue-Langevin.
YbRh2Si2 emerged in the context of investigations into rare-earth intermetallics alongside materials such as CeCu6, CeRhIn5, and URu2Si2. It crystallizes in a tetragonal lattice similar to the ThCr2Si2 structure type, which connects it to families studied by researchers at the Paul Scherrer Institute and the Los Alamos National Laboratory. Early experiments highlighting non-Fermi-liquid signatures and extremely low magnetic ordering temperatures were reported by collaborations between groups in Göttingen, Dresden, and Zurich, prompting comparative work with prototypes like YbAl3 and YbCuAl.
YbRh2Si2 adopts a body-centered tetragonal structure in the space group I4/mmm, the same structural family as BaFe2As2 and other 122 compounds. Single crystals are commonly grown using flux methods (e.g., indium or tin flux), Bridgman techniques, or high-temperature solution growth employed in laboratories at ETH Zurich and the Fritz Haber Institute. X-ray diffraction studies performed at beamlines of the European Synchrotron Radiation Facility and neutron diffraction experiments at the Institut Laue-Langevin have been used to characterize lattice parameters, atomic positions, and residual resistivity ratios, enabling comparisons with structural refinements reported for ThCr2Si2-type materials. High-purity ytterbium sources from suppliers used by groups at Oak Ridge National Laboratory and NIST are essential to minimize site disorder observed in earlier growth trials.
The electronic structure of YbRh2Si2 shows heavy quasiparticle masses derived from hybridization between localized 4f electrons of ytterbium and conduction electrons of rhodium and silicon, analogous to behavior in Ce-based heavy fermion systems such as CeCu2Si2. Angle-resolved photoemission spectroscopy performed at the Synchrotron Radiation Source and de Haas–van Alphen measurements at high-field laboratories including Helmholtz-Zentrum Dresden-Rossendorf reveal a Fermi surface strongly renormalized compared with band-structure calculations from groups using methods developed in Princeton University and Stanford University. Magnetization and specific heat measurements carried out by research teams at Leiden University and the Royal Society laboratories show a tiny antiferromagnetic ordering below about 70 mK, with susceptibility and Sommerfeld coefficient behavior comparable to findings in UPt3 and CeAl3.
YbRh2Si2 is a canonical system for studying quantum critical points where antiferromagnetic order is suppressed to zero temperature by tuning parameters such as magnetic field or chemical pressure, paralleling themes from the Hertz–Millis and Si–Coleman debates. Experiments demonstrating non-Fermi-liquid resistivity, logarithmic divergences in specific heat, and changes in Hall coefficient were reported by teams collaborating across MPI PKS and University of Augsburg, stimulating theoretical work by groups at MIT, University of Cambridge, and Rutgers University. The material has been central to discussions about local quantum criticality, Fermi-surface reconstruction, and critical quasiparticles that relate to proposals from Qimiao Si, Philipp Gegenwart, and Piers Coleman.
Investigations of YbRh2Si2 employ low-temperature cryogenic platforms such as dilution refrigerators and adiabatic demagnetization systems available at facilities like CEA Grenoble and Riken. Measurements include electrical resistivity, thermal expansion, and magnetotransport performed in high-field magnets at the National High Magnetic Field Laboratory and quantum oscillation studies using torque magnetometry in collaboration with groups at Los Alamos National Laboratory. Neutron scattering at the Institut Laue-Langevin and muon spin rotation carried out at the Paul Scherrer Institute probe magnetic correlations, while resonant inelastic x-ray scattering at synchrotron facilities compares 4f spectral weight to theoretical predictions from groups at Brookhaven National Laboratory and Lawrence Berkeley National Laboratory.
Theoretical descriptions of YbRh2Si2 draw on multi-orbital Anderson and Kondo lattice Hamiltonians developed in the theoretical programs at University of California, Los Angeles and Yale University. Competing frameworks include spin-density-wave approaches associated with the Hertz–Millis formulation and local criticality scenarios advocated by researchers at Rice University and Iowa State University. Quantum Monte Carlo, dynamical mean-field theory, and renormalization-group analyses from teams at ETH Zurich and MPIPKS attempt to reconcile thermodynamic singularities, transport anomalies, and Hall-effect measurements, engaging debates prominent at conferences hosted by the American Physical Society and International Conference on Strongly Correlated Electron Systems.
Related rare-earth 122 compounds include CeRh2Si2, BaFe2As2, and substituted variants such as Yb(Rh1−xCox)2Si2 and YbRh2(Si1−xGex)2 investigated at laboratories including CEA Saclay and Kavli Institute. While direct technological applications are limited, insights from YbRh2Si2 inform understanding of unconventional superconductivity in materials like CeCoIn5 and guide exploratory materials design pursued at institutions such as IBM Research and Toyota Central R&D Labs. The compound remains a benchmark for testing ideas relevant to quantum materials programs funded by agencies including the European Research Council and the Deutsche Forschungsgemeinschaft.
Category:Intermetallic compounds Category:Heavy fermion compounds