Instability of the f -electron state in URu2Si2−xPx probed using high magnetic fields

Abstract

The widely studied Hidden Order phase in URu2Si2 exemplifies a broad class of emergent macroscopic states originating from dand f -electron orbitals and their collective modes. This naturally has resulted in a focus on the associated elements (i.e., U and Ru), but recently it was discovered that electronic tuning on the more passive sand p-orbitals fundamentally alters the electronic behavior and thus opens opportunities to disentangle the Hidden Order conundrum. Here we present a detailed magnetoresistivity study of URu2Si2−xPx which focuses on two important aspects of this topic. First, we show that the anisotropy of the high field ordered states is preserved after Hidden Order is destroyed by Si → P chemical substitution, suggesting that this feature is mainly associated with the Kondo lattice; i.e., not Hidden Order itself. Second, Shubnikov-de Haas oscillations reveal that the observable parts of the Fermi surface topography are robust upon approaching the Hidden Order phase boundary and the associated quasiparticle masses remains roughly constant. These observations place constraints on theories and prepare a path towards a resolution to the Hidden Order problem.

Electronic Tuning in URu2Si2 Through Ru to Pt Chemical Substitution

“…Finally, for x ≈ 0.19, ρ/ρ 300K decreases weakly with H until it undergoes a more rapid reduction near 33 T, indicating the occurrence of a metamagnetic phase transition. This is similar to what was earlier seen in the antiferromagnetic x region for the Si → P series (Wartenbe et al, 2017;Huang et al, 2019), although the critical field is substantially reduced.…”

“…The behavior for x ≈ 0.03 is distinct from what is seen in the HO x region. Here, the initial increase in ρ/ρ 300K is weak and there is an abrupt increase near 31 T that is followed by an abrupt decrease at 38 T. This square shape curve is reminiscent of what was previously seen in Si → P (Wartenbe et al, 2017;Huang et al, 2019) and Ru → Rh (Kuwahara et al, 2013) substitution series within the x range that hosts a paramagnetic Kondo lattice without long-range ordered ground states. Finally, for x ≈ 0.19, ρ/ρ 300K decreases weakly with H until it undergoes a more rapid reduction near 33 T, indicating the occurrence of a metamagnetic phase transition.…”

Hidden order and beyond: an experimental—theoretical overview of the multifaceted behavior of URu2Si2

“…However, for x = 0.09 no long-range AFM but only a seared tendency towards AFM regions. In the most recent work high magnetic fields were used to determine the effects of P substitution [213]. It would seem that the larger P atoms modify the position of Si sites and via strain fields detune the crystal structure and FS that causes a four-fold to two-fold symmetry breaking and, accordingly, the formation of the AFM state.…”

Collinear antiferromagnetic order in URu2Si2−xPx revealed by neutron diffraction

“…In particular, the superconducting critical temperature T c ≈ 1.4 K weakly increases to a maximum at x ≈ 0.01, before suppression of SC at x ≈ 0.028 and suppression of HO at x ≈ 0.035 [60]. Quantum oscillation measurements in this regime indicate that no significant changes of the Fermi surface are associated with the destruction of the HO phase [64]. Following a paramagnetic Kondo lattice state in the range 0.035 x 0.26, antiferromagnetism is abruptly stabilized at x 0.27 [59].…”