257 research outputs found
Similarity of Fermi Surface in the Hidden Order State and in the Antiferromagnetic State of URu2Si2
Shubnikov-de Haas measurements of high quality URu2Si2 single crystals reveal
two previously unobserved Fermi surface branches in the so-called hidden order
phase. Therefore about 55% of the enhanced mass is now detected. Under pressure
in the antiferromagnetic state, the Shubnikov-de Haas frequencies for magnetic
fields applied along the crystalline c axis show little change compared with
the zero pressure data. This implies a similar Fermi surface in both the hidden
order and antiferromagnetic states, which strongly suggests that the lattice
doubling in the antiferromagnetic phase due to the ordering vector QAF = (0 0
1) already occurs in the hidden order. These measurements provide a good test
for existing or future theories of the hidden order parameter.Comment: 4 pages, 4 figure
Probing the extended non-Fermi liquid regimes of MnSi and Fe
Recent studies show that the non-Fermi liquid (NFL) behavior of MnSi and Fe
spans over an unexpectedly broad pressure range, between the critical pressure
p_c and around 2p_c. In order to determine the extension of their NFL regions,
we analyze the evolution of the resistivity rho(T) A(p)T^n at higher pressures.
We find that in MnSi the n=3/2 exponent holds below 4.8 GPa=3 p_c, but it
increases above that pressure. At 7.2 GPa we observe the low temperature Fermi
liquid exponent n=2 whereas for T>1.5 K, n=5/3. Our measurements in Fe show
that the NFL behavior rho T^{5/3} extends at least up to 30.5 GPa, above the
entire superconducting (SC) region. In the studied pressure range, the onset of
the SC transition reduces by a factor 10 down to T_c^onset(30.5 GPa)=0.23 K,
while the A-coefficient diminishes monotonically by around 50%.Comment: 2 pages, 2 figures, Proceedings SCES 200
Tunneling spectroscopy of the superconducting state of URu2Si2
We present measurements of the superconducting gap of URuSi made with
scanning tunneling microscopy (STM) using a superconducting tip of Al. We find
tunneling conductance curves with a finite value at the Fermi level. The
density of states is V shaped at low energies, and the quasiparticle peaks are
located at values close to the expected superconducting gap from weak coupling
BCS theory. Our results point to rather opened gap structures and gap nodes on
the Fermi surface
- …