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Critical slowing down of fermions near a magnetic quantum phase transition
- Publication Year :
- 2022
-
Abstract
- A universal phenomenon in phase transitions is critical slowing down (CSD) - systems, after an initial perturbation, take an exceptionally long time to return to equilibrium. It is universally observed in the dynamics of bosonic excitations, like order-parameter collective modes, but it is not generally expected to occur for fermionic excitations because of the half-integer nature of the fermionic spin. Direct observation of CSD in fermionic excitations or quasiparticles would therefore be of fundamental significance. Here, we observe fermionic CSD in the heavy-fermion (HF) compound YbRh$_2$Si$_2$ by terahertz time-domain spectroscopy. HFs are compound objects with a strongly enhanced effective mass, composed of itinerant and localized electronic states. We see that near the quantum phase transition in YbRh$_2$Si$_2$ the build-up of spectral weight of the HFs towards the Kondo temperature $T_K\approx 25$ K is followed by a logarithmic rise of the quasiparticle excitation rate on the heavy-Fermi-liquid side of the quantum phase transition below $10$ K. A critical two-band HF liquid theory shows that this is indicative of fermionic CSD. This CSD is a clear indication that the HF quasiparticles experience a breakdown near the quantum phase transition, and the critical exponent of this breakdown introduces a classification of fermionic quantum phase transitions analogous to thermodynamic phase transitions - solution to a long-standing problem.<br />Comment: 6 pages, 4 figures. Nature Phys. (2023)
- Subjects :
- Condensed Matter - Strongly Correlated Electrons
Physics - Optics
Subjects
Details
- Database :
- arXiv
- Publication Type :
- Report
- Accession number :
- edsarx.2208.05932
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1038/s41567-023-02156-7