%0 Journal Article %1 Kaminski2002 %A Kaminski, A. %A Rosenkranz, S. %A Fretwell, H. M. %A Campuzano, J. C. %A Li, Z. %A Raffy, H. %A Cullen, W. G. %A You, H. %A Olson, C. G. %A Varma, C. M. %A Hochst, H. %D 2002 %J Nature %K imported %N 6881 %P 610--613 %T Spontaneous breaking of time-reversal symmetry in the pseudogap state of a high-Tc superconductor %U http://dx.doi.org/10.1038/416610a %V 416 %X A change in 'symmetry' is often observed when matter undergoes a phase transition—the symmetry is said to be spontaneously broken. The transition made by underdoped high-transition-temperature (high-$T_c$) superconductors is unusual, in that it is not a mean-field transition as seen in other superconductors. Rather, there is a region in the phase diagram above the superconducting transition temperature $T_c$ (where phase coherence and superconductivity begin) but below a characteristic temperature $T*$ where a 'pseudogap' appears in the spectrum of electronic excitations$^1, 2$. It is therefore important to establish if $T*$ is just a cross-over temperature arising from fluctuations in the order parameter that will establish superconductivity at $T_c$ (refs 3, 4), or if it marks a phase transition where symmetry is spontaneously broken$^5, 6, 7, 8, 9, 10$. Here we report that, for a material in the pseudogap state, left-circularly polarized photons give a different photocurrent from right-circularly polarized photons. This shows that time-reversal symmetry is spontaneously broken$^11$ below $T*$, which therefore corresponds to a phase transition.

@article{Kaminski2002, abstract = {A change in 'symmetry' is often observed when matter undergoes a phase transition—the symmetry is said to be spontaneously broken. The transition made by underdoped high-transition-temperature (high-$T_c$) superconductors is unusual, in that it is not a mean-field transition as seen in other superconductors. Rather, there is a region in the phase diagram above the superconducting transition temperature $T_c$ (where phase coherence and superconductivity begin) but below a characteristic temperature $T*$ where a 'pseudogap' appears in the spectrum of electronic excitations$^{1, 2}$. It is therefore important to establish if $T*$ is just a cross-over temperature arising from fluctuations in the order parameter that will establish superconductivity at $T_c$ (refs 3, 4), or if it marks a phase transition where symmetry is spontaneously broken$^{5, 6, 7, 8, 9, 10}$. Here we report that, for a material in the pseudogap state, left-circularly polarized photons give a different photocurrent from right-circularly polarized photons. This shows that time-reversal symmetry is spontaneously broken$^{11}$ below $T*$, which therefore corresponds to a phase transition.}, added-at = {2010-11-06T00:14:39.000+0100}, author = {Kaminski, A. and Rosenkranz, S. and Fretwell, H. M. and Campuzano, J. C. and Li, Z. and Raffy, H. and Cullen, W. G. and You, H. and Olson, C. G. and Varma, C. M. and Hochst, H.}, biburl = {https://www.bibsonomy.org/bibtex/264df221ac7efdd4da8f65904f892f171/nplumb}, comment = {10.1038/416610a}, file = {:C\:\\Users\\Nick\\Documents\\Papers\\Kaminski et al. - Spontaneous breaking of time-reversal symmetry in the pseudogap state of a high-Tc superconductor.pdf:PDF}, interhash = {44b516426546cfe3b02d1528c76fc633}, intrahash = {64df221ac7efdd4da8f65904f892f171}, issn = {0028-0836}, journal = {Nature}, keywords = {imported}, month = apr, number = 6881, owner = {Nick}, pages = {610--613}, timestamp = {2010-11-06T00:14:41.000+0100}, title = {Spontaneous breaking of time-reversal symmetry in the pseudogap state of a high-Tc superconductor}, url = {http://dx.doi.org/10.1038/416610a}, volume = 416, year = 2002 }