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Thursday, April 28, 2011
2:00 PM - 3:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Postdoc Seminar

How to probe a quantum critical point from thermodynamics

Lijun Zhu
T-4 and CNLS

A quantum critical point (QCP) arises when matter undergoes a continuous phase transition at zero temperature tuned by a nonthermal physical parameter. Strong quantum fluctuations around a QCP lead to novel physical properties at finite temperatures. I show that in thermodynamics, the Grueneisen ratio, a ratio between thermal expansion (as the variation of entropy with the tuning parameter) and the specific heat, diverges at and only at QCPs. Its temperature exponent provides classification of QCPs. Also accompanied is the entropy accumulation effect. These thermodynamic features provide a systematic probe to QCPs in experiments. I will illustrate these features from a scaling analysis and modeled calculations for magnetic QCPs. I will also show experimental examples in heavy fermion metals and ruthenates.

Host: Peter Loxley, loxley@lanl.gov