Systematic study of the Grüneisen ratio near quantum critical points
At any pressure-sensitive quantum critical point (QCP), the volume thermal expansion coefficient is more singular than the specific heat. Consequently, the resulting critical Grüneisen ratio Γcr~βcr/Ccr, where βcr and Ccr denote the thermal expansion and specific heat after subtraction of non-critic...
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| Format: | Article |
| Language: | English |
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Taylor & Francis Group
2007-01-01
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| Series: | Science and Technology of Advanced Materials |
| Online Access: | http://www.iop.org/EJ/abstract/1468-6996/8/5/A17 |
| Summary: | At any pressure-sensitive quantum critical point (QCP), the volume thermal expansion coefficient is more singular than the specific heat. Consequently, the resulting critical Grüneisen ratio Γcr~βcr/Ccr, where βcr and Ccr denote the thermal expansion and specific heat after subtraction of non-critical background contributions, diverges. The related critical exponent epsilon in Γcr~T−epsilon can be used to characterize the nature of the underlying quantum critical fluctuations. We have performed a comparative study on various heavy fermion (HF) systems close to antiferromagnetic QCPs. In particular, we have studied (i) CeIn3−xSnx, (ii) CeNi2Ge2, (iii) YbRh2(Si0.95Ge0.05)2, as well as (iv) CeCu5.8Ag0.2, all of which show a divergent Grüneisen ratio. For the two former systems the critical exponent epsilon=1 is compatible with the predictions of the well-established Hertz–Millis–Moriya theory for three-dimensional extended quantum critical fluctuations. By contrast, for the two latter systems epsilon<1 is found to be incompatible with "conventional" quantum criticality. Our results thus suggest the existence of at least two different classes of QCPs in HF systems. |
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| ISSN: | 1468-6996 1878-5514 |