Critical slowing down of fermions near a magnetic quantum phase transition
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arXiv
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| Autori principali: | , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2022
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| _version_ | 1866912027274903552 |
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| author | Yang, Chia-Jung Kliemt, Kristin Krellner, Cornelius Kroha, Johann Fiebig, Manfred Pal, Shovon |
| author_facet | Yang, Chia-Jung Kliemt, Kristin Krellner, Cornelius Kroha, Johann Fiebig, Manfred Pal, Shovon |
| contents | 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2208_05932 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Critical slowing down of fermions near a magnetic quantum phase transition Yang, Chia-Jung Kliemt, Kristin Krellner, Cornelius Kroha, Johann Fiebig, Manfred Pal, Shovon Strongly Correlated Electrons Optics 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. |
| title | Critical slowing down of fermions near a magnetic quantum phase transition |
| topic | Strongly Correlated Electrons Optics |
| url | https://arxiv.org/abs/2208.05932 |