title: Analogy Between the "Hidden Order" and the Orbital Antiferromagnetism in URu_{2-x}Fe_{x}Si_{2}.
abstract: We study URu_{2-x}Fe_{x}Si_{2}, in which two types of staggered phases compete at low temperature as the iron concentration x is varied: the nonmagnetic "hidden order" (HO) phase below the critical concentration x_{c}, and unconventional antiferromagnetic (AFM) phase above x_{c}. By using polarization resolved Raman spectroscopy, we detect a collective mode of pseudovectorlike A_{2g} symmetry whose energy continuously evolves with increasing x; it monotonically decreases in the HO phase until it vanishes at x=x_{c}, and then reappears with increasing energy in the AFM phase. The mode's evolution provides direct evidence for a unified order parameter for both nonmagnetic and magnetic phases arising from the orbital degrees-of-freedom of the uranium-5f electrons.
authors.affiliation: Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: H-H
authors.initials: HH
authors.lastname: Kung
authors.affiliation: Department of Physics, University of California San Diego, La Jolla, California 92093, USA.|Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ran
authors.affiliation: Department of Physics, University of California San Diego, La Jolla, California 92093, USA.|Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA.
authors.forename: N
authors.initials: N
authors.lastname: Kanchanavatee
authors.affiliation: Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: V
authors.initials: V
authors.lastname: Krapivin
authors.affiliation: Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lee
authors.affiliation: Kamerlingh Onnes Laboratory, Leiden University, 2300 RA Leiden, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: Mydosh
authors.affiliation: Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: K
authors.initials: K
authors.lastname: Haule
authors.affiliation: Department of Physics, University of California San Diego, La Jolla, California 92093, USA.|Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Maple
authors.affiliation: Department of Physics & Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.|National Institute of Chemical Physics and Biophysics, 12618 Tallinn, Estonia.
authors.forename: G
authors.initials: G
authors.lastname: Blumberg