### Session X8: Focus Session: Novel Superconductors VII: Triplet Pairing and Time Reversal Symmetry Breaking

8:00 AM–11:00 AM, Friday, March 9, 2007
Colorado Convention Center Room: Korbel 1C

Chair: Igor Mazin, Naval Research Laboratory

Abstract ID: BAPS.2007.MAR.X8.9

### Abstract: X8.00009 : High Resolution Polar Kerr Effect Measurements of High-Temperature Superconductors: Evidence for Broken Time Reversal Symmetry Below the Pseudogap temperature

10:00 AM–10:12 AM

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#### Authors:

Elizabeth Schemm
(Stanford University)

Jing Xia
(Stanford University)

Wolter Siemons
(Stanford University)

Gertjan Koster
(Stanford University)

Martin M. Fejer
(Stanford University)

Aharon Kapitulnik
(Stanford University)

High resolution Polar Kerr Effect (PKE) measurements were performed on YBa$_2$Cu$_3$O$_{7-\delta}$ as a function of temperature for variety of doping levels. In order be able to measure effects beyond our old search for anyon superconductivity, we devised a new technique based on a fiber Sagnac interferometer with a zero-area Sagnac loop. With this technique we show a shotnoise-limited sensitivity of 100 nanorad/$\sqrt{Hz}$ with incident photon power of $\sim$ 10 $\mu$-Watt, in a wide temperature range from 0.3 K to room temperature. Our results indicate that a Time Reversal Symmetry Breaking (TRSB) signal appears in all underdoped YBa$_2$Cu$_3$O$_{7-\delta}$~ samples below the doping dependent pseudogap temperature. The effect increases with decreasing temperature and seems to saturate at a lower temperature close to $T_c$. The saturated size of the effect increases with increasing $\delta$. We will discuss possible origins of this effect and its presence in other high-Tc superconductors.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.X8.9