Events at Physics

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Events on Monday, October 7th, 2013

Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:30 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (
Host: Peter Timbie
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Condensed Matter Theory Group Seminar
Superconductivity at the onset of spin-density-wave order in a metal
Time: 4:30 pm
Place: Chamberin 5310
Speaker: Yuxuan Wang, Physics Department
Abstract: We revisit the issue of superconductivity at the quantum-critical point between a 2D paramagnet and a spin-density-wave (SDW) metal with ordering momentum (pi,pi). This problem is highly non-trivial because the system at criticality displays a non-Fermi liquid behavior and because the effective coupling constant &amp;amp;#955; for the pairing is generally of order one, even when the actual interaction is smaller than fermionic bandwidth. Previous study [M. A. Metlitski, S. Sachdev, Phys.Rev.B 82, 075128 (2010)]has found that the leading renormalization of the pairing vertex contains log2, like in color superconductivity. We analyze the full gap equation and argue that summing up log2 term does not lead to a pairing instability. Yet, superconductivity has no threshold, even if &amp;amp;#955; is set to be small: the subleading log terms give rise to BCS-like Tc&amp;amp;#8733;e&amp;amp;#8722;1/&amp;amp;#955;. We argue that the analogy with BCS is not accidental as superconductivity at a QCP is a Fermi liquid phenomenon -- it comes from fermions which retain Fermi liquid behavior at criticality. We compute Tc for the actual &amp;amp;#955; and find consistency with the numerical results.<br>
Host: Natalia Perkins
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