Phase transitions and suppression of magnetoresistance in WTe2-xSesystem.

X-ray diffraction, Raman spectroscopy, and electrical resistivity measurements on polycrystalline WTe2-xSe(0 ⩽ x ⩽ 0.8) reveal a-1T'structural phase transition and suppression of magnetoresistance at = 0.2.

From hidden order to antiferromagnetism: Electronic structure changes in Fe-doped URuSi.

In matter, any spontaneous symmetry breaking induces a phase transition characterized by an order parameter, such as the magnetization vector in ferromagnets, or a macroscopic many-electron wave function in superconductors. Phase transitions with unknown order parameter are rare but extremely appealing, as they may lead to novel physics. An emblematic and still unsolved example is the transition of the heavy fermion compound [Formula: see text] (URS) into the so-called hidden-order (HO) phase when the temperature drops below [Formula: see text] K.

Isoelectronic perturbations to --electron hybridization and the enhancement of hidden order in URuSi.

Electrical resistivity measurements were performed on single crystals of URu Os Si up to = 0.28 under hydrostatic pressure up to = 2 GPa. As the Os concentration, , is increased, 1) the lattice expands, creating an effective negative chemical pressure (); 2) the hidden-order (HO) phase is enhanced and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase; and 3) less external pressure is required to induce the HO→LMAFM phase transition.

Phase diagram of URu Fe Si in high magnetic fields.

Electrical transport measurements were performed on URu Fe Si single-crystal specimens in high magnetic fields up to 45 T (DC fields) and 60 T (pulsed fields). We observed a systematic evolution of the critical fields for both the hidden-order (HO) and large-moment antiferromagnetic (LMAFM) phases and established the 3D phase diagram of In the HO phase, / scales with / and collapses onto a single curve. However, in the LMAFM phase, this single scaling relation is not satisfied.

Analogy Between the "Hidden Order" and the Orbital Antiferromagnetism in URu_{2-x}Fe_{x}Si_{2}.

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.