2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session Q2: New Insights into Hidden Order in URu2Si2
11:15 AM–1:39 PM,
Wednesday, March 18, 2009
Room: Spirit of Pittsburgh Ballroom BC
Sponsoring
Unit:
DCMP
Chair: John Mydosh, Leiden University
Abstract ID: BAPS.2009.MAR.Q2.4
Abstract: Q2.00004 : Competition of Hidden Order and Antiferromagnetism in URu$_2$Si$_2$ under Pressure
1:03 PM–1:39 PM
Preview Abstract
Abstract
Author:
Elena Hassinger
(INAC, CEA Grenoble, France)
URu$_2$Si$_2$ is a heavy fermion compound with an ordered phase
below $T_0=17.5$~K at ambient pressure.
The signature of the transition at $T_0$ in macroscopic
quantities is very large and indicates a partial gap opening on
the Fermi surface. However, the order parameter could not be
identified yet and therefore, the phase is called hidden order (HO).
Additionally, the compound becomes superconducting below
$T_{sc}=1.4$~K. Here, we\footnote{Collaborators : A. Villaume, G.
Knebel, F. Bourdarot, V. Taufour, S. Raymond, J. Flouquet} focus
on the difference between HO and
the pressure induced antiferromagnetic state (AF) in order to
shed light on the HO itself.
By specific heat and resistivity measurements under
pressure\footnote{E. Hassinger {\em et al.}, Phys. Rev. B
\textbf{77}, 115117 (2008)}, we were able to confirm the
pressure-temperature phase diagram determined by neutron
scattering\footnote{H. Amitsuka {\em et al.}, J. Magn. Magn.
Mater. \textbf{310}, 214 (2007)}. For pressures higher than
$P_c=0.5$~GPa
the antiferromagnetic phase develops and superconductivity is
suppressed at the same time. The transition line between HO and
AF can be seen as a small anomaly in resistivity and specific
heat data until 1.3~GPa, where it seems to join the transition
line between the paramagnetic and the HO phase. The nesting-like
signature at $T_0$ in resistivity surprisingly does not change
qualitatively between low pressures at the transition to HO and
high pressures at the transition to the AF. The differences in
the low energy excitations between the HO and AF phases have been
investigated by neutron scattering measurements at
0.67~GPa\footnote{A. Villaume {\em et al.}, Phys. Rev. B
\textbf{78}, 012504 (2008)}, where three phases can be detected
on cooling: paramagnetic, HO and AF phase. The inelastic response
at the antiferromagnetic wavevector $Q_0=(1,0,0)$ and at the
position of the second minimum in the dispersion relation
$Q_1=(1.4,0,0)$ was measured in the three distinct phases. The
sharp excitation at $Q_0$ with a gap of 1.8~meV exists only in
the hidden order phase and disappears in the antiferromagnetic
phase whereas the excitation at $Q_1$ persists in both phases.
Therefore only the excitations at the commensurate wavevector
$Q_0$ are characteristic of the HO phase.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.Q2.4