University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Monday, December 8th 2014
1:00 pm:
CM Journal Club in 210 Tate
Speaker: Tianbai Cui
Subject: Griffith Effects at Classical and Quantum Phase Transitions

Phase transitions in a quenched disordered system behave differently from the ones in a clean system. One interesting aspect of this is the Griffiths effect, namely, the properties of the phase transition can be dramatically changed by the fluctuations of the rare large spatial regions (the so call “rare regions”) that are devoid of impurities. In generic classical systems, the Griffiths effects are very weak, therefore, were seldom observed in experiments. For quantum phase transitions, however, the Griffiths phenomena are enhanced, which can lead to power-law singularities in thermodynamic quantities. I will qualitatively talk about the Griffith effect in classical phase transitions by considering a randomly diluted Ising model. Then, I will talk about the quantum Griffiths effects by studying quantum phase transitions in itinerant magnets with Heisenberg spin symmetry in the large-N limit. References: [1] T. Vojta, J. Phys. A 39, R143 (2006). [2] T. Vojta and J. Schmalian, Phys. Rev. B 72, 045438 (2005).

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