A ferromagnetic quantum critical point is thought not to exist in two-and three-dimensional metallic systems yet is realized in the Kondo lattice compound YbNi4(P, As)(2), possibly due to its ...onedimensionality. It is crucial to investigate the dimensionality of the Fermi surface of YbNi4 P-2 experimentally, but common probes such as angle-resolved photoemission spectroscopy and quantum oscillation measurements are lacking. Here, we study the magnetic-field dependence of transport and thermodynamic properties of YbNi4 P-2. The Kondo effect is continuously suppressed, and additionally we identify nine Lifshitz transitions between 0.4 and 18 T. We analyze the transport coefficients in detail and identify the type of Lifshitz transitions as neck or void type to gain information on the Fermi surface of YbNi4P2. The large number of Lifshitz transitions observed within this small energy window is unprecedented and results from the particular flat renormalized band structure with strong 4f-electron character shaped by the Kondo lattice effect.
Abstract
We present the crystal growth as well as the structural, chemical and physical chracterization of SmRh
2
Si
2
single crystals. Their ground state is antiferromagnetic, as indicated by the ...behaviour of the magnetic susceptibility and the specific heat at the second order phase transition observed at
T
N
= 64 K. The Sommerfeld coefficient is small and similar to that of LuRh
2
Si
2
with
γ
0
≈
7
mJ/(molK
2
). Susceptibility measurements show no Curie-Weiss behaviour at high temperatures which is a consequence of the large Van-Vleck contribution of the excited multiplets of Sm
3+
. Previous angle-resolved photoemission studies showed that at 10 K, the valence of the Sm ions is smaller than three at the surface as well as in the bulk, suggesting a possible Kondo screening of the Sm
3+
ions. This could not be observed in our thermodynamic and transport measurements.
The discovery of a square magnetic-skyrmion lattice in GdRu 2 Si 2 , with the smallest so far found skyrmion size and without a geometrically frustrated lattice, has attracted significant attention. ...In this work, we present a comprehensive study of surface and bulk electronic structures of GdRu 2 Si 2 by utilizing momentum-resolved photoemission (ARPES) measurements and first-principles calculations. We show how the electronic structure evolves during the antiferromagnetic transition when a peculiar helical order of 4f magnetic moments within the Gd layers sets in. A nice agreement of the ARPES-derived electronic structure with the calculated one has allowed us to characterize the features of the Fermi surface (FS), unveil the nested region along k z at the corner of the 3D FS, and reveal their orbital compositions. Our findings suggest that the Ruderman–Kittel–Kasuya–Yosida interaction plays a decisive role in stabilizing the spiral-like order of Gd 4f moments responsible for the skyrmion physics in GdRu 2 Si 2 . Our results provide a deeper understanding of electronic and magnetic properties of this material, which is crucial for predicting and developing novel skyrmion-based systems.
The nature of the antiferromagnetic order in the heavy fermion metal YbRh_{2}Si_{2}, its quantum criticality, and superconductivity, which appears at low mK temperatures, remain open questions. We ...report measurements of the heat capacity over the wide temperature range 180 μK-80 mK, using current sensing noise thermometry. In zero magnetic field we observe a remarkably sharp heat capacity anomaly at 1.5 mK, which we identify as an electronuclear transition into a state with spatially modulated electronic magnetic order of maximum amplitude 0.1 μ_{B}. We also report results of measurements in magnetic fields in the range 0 to 70 mT, applied perpendicular to the c axis, which show eventual suppression of this order. These results demonstrate a coexistence of a large moment antiferromagnet with putative superconductivity.
The discovery of a square magnetic-skyrmion lattice in GdRu
2
Si
2
, with the smallest so far found skyrmion size and without a geometrically frustrated lattice, has attracted significant attention. ...In this work, we present a comprehensive study of surface and bulk electronic structures of GdRu
2
Si
2
by utilizing momentum-resolved photoemission (ARPES) measurements and first-principles calculations. We show how the electronic structure evolves during the antiferromagnetic transition when a peculiar helical order of 4f magnetic moments within the Gd layers sets in. A nice agreement of the ARPES-derived electronic structure with the calculated one has allowed us to characterize the features of the Fermi surface (FS), unveil the nested region along
k
z
at the corner of the 3D FS, and reveal their orbital compositions. Our findings suggest that the Ruderman-Kittel-Kasuya-Yosida interaction plays a decisive role in stabilizing the spiral-like order of Gd 4f moments responsible for the skyrmion physics in GdRu
2
Si
2
. Our results provide a deeper understanding of electronic and magnetic properties of this material, which is crucial for predicting and developing novel skyrmion-based systems.
A combination of momentum-resolved photoemission measurements and first-principles calculations allowed us to unveil the origin of the helical magnetic order in the GdRu
2
Si
2
skyrmion magnet.
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