Temperautre dependence of the low-energy electronic structure of Ca₃Ru₂O₇

We use angular-resolved photoemission spectroscopy (ARPES) and ab initio calculations to study the low-energy electronic band structure of a bilayer ruthenate system, Ca₃Ru₂O₇, across a wide temperature range. Ca₃Ru₂O₇ is a bad metal which undergoes two magnetic transitions [1]: a Néel ordering at 56 K and a spin-reorientation with a coupled structural transition at 48 K. At low temperatures we find it to be a compensated semimetal, in general agreement with previous ARPES [2] and de Haas-van Alphen [3] experiments. Our measurements across the 48 K transition, however, reveal dramatic changes in the low-energy electronic structure in terms of the shape and size of the Fermi surface. This is accompanied by a significant increase in the scattering rate, and our temperature-dependent ARPES suggests new insights into the unusual transport properties of this system in its “bad metal” phase. We further explore the role of crystal structure, magnetism, and spin-orbit coupling in the evolution of the electronic structure across the 48 K phase transition.

[1] Cao, et al., PRL 78 (1997) 1751
[2] Baumberger et al., PRL 96 (2006) 107601
[3] Kikugawa et al., JPSJ 79 (2010) 024704