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We report first-principles and strongly-correlated calculations of the newly-discovered heavy fermion superconductor UTe2. Our analyses reveal three key aspects of its magnetic, electronic, and superconducting properties, that include: (1) a two-leg ladder-type structure with strong magnetic frustrations, which might explain the absence of long-range orders and the observed magnetic and transport anisotropy; (2) quasi-two-dimensional Fermi surfaces composed of two separate electron and hole cylinders with similar nesting properties as in UGe2, which may potentially promote magnetic fluctuations and help to enhance the spin-triplet pairing; (3) a unitary spin-triplet pairing state of strong spin-orbit coupling at zero field, with point nodes presumably on the heavier hole Fermi surface along the kx-direction, in contrast to the previous belief of non-unitary pairing. Our proposed scenario is in excellent agreement with latest thermal conductivity measurement and provides a basis for understanding the peculiar magnetic and superconducting properties of UTe2.

We utilized high-resolution resonant angle-resolved photoemission spectroscopy (ARPES) to study the band structure and hybridization effect of the heavy-fermion compound Ce2IrIn8. We observe a nearly flat band at the binding energy of 7 meV below the coherent temperature Tcoh~40 K, which characterizes the electrical resistance maximum indicating the onset temperature of hybridization. However, the Fermi vector kF and the Fermi surface (FS) volume have little change around Tcoh, challenging the widely believed evolution from a high-temperature small FS to a low-temperature large FS. Our experimental results of the band structure fit well with the density functional theory plus dynamic mean-field theory (DFT+DMFT) calculations. INTRODUCTION:Heavy-fermion compounds, first discovered in CeAl3 in 1975 [1], are some of the most exotic materials in condensed matter physics. The name originates from the largely enhanced effective mass of the heavy quasi-particles, which can be 2 or 3 orders of magnitude higher than that in a normal metal [2]. These compounds usually contain some of Ce, Sm, Yb, U, Pr, Pu, Np elements, which possess an unfilled 4f or 5f shell. It is widely believed that 4f/5f electrons are local moments at high temperatures and become itinerant after hybridized with the conduction electrons at low temperatures. Varieties of phenomena, e.g., antiferromagnetism [3], ferromagnetism [4], superconductivity [5], quantum critical point [6], quadrupole order [7], hidden order [8-9], topological property [10], have been discovered in heavy-fermion compounds. Central to understanding these exotic phenomena is the interplay of itinerancy and localization. However, the low energy scales (critical temperature, hybridization gap, superconducting gap) in heavy-fermion systems have brought major challenges to many experimental techniques.CemTnIn3m+2n (m = 1, 2; n = 1, 2 and T: Co, Rh, Ir, Pd, Pt) family is a good platform of heavy-fermion materials for studying the interplay between c-f hybridization, magnetism, superconductivity, quantum criticality, and etc. CemTnIn3m+2n crystallizes with a tetragonal unit cell that can be viewed as m-layers of CeIn3 unit stacked sequentially with intervening n-layers of TIn2 along the c-axis. Among them, the spin-glass state observed in Ce2IrIn8 indicates partially delocalized Ce 4f electron [11]. The magnetism in Ce2IrIn8 depends on Ce-Ir hybridization and local Ce environment. The small but finite onset temperature for spin freezing rules out the quantum critical point (QCP) scenario in Ce2IrIn8 [11]. High Sommerfeld coefficient (γ~700 mJ/mol‧K 2 ) [12] and the absence of long-range magnetic order indicate an itinerant behavior of Ce 4f electron. μSR observed a 'Knight-shift anomaly' in which the Knight shift constant K no longer scales linearly with the susceptibility below a characteristic temperature Tcoh, in agreement with the "two-fluid" model of heavy-fermion formation [15]. Resistivity measurements showed a broad maximum near 40 -50 K [13,16], manifesting the development of a...

We report a detailed and comparative study of the single crystal CeCoInGa3 in both experiment and theory. Resistivity measurements reveal the typical behavior of Kondo lattice with the onset temperature of coherence, T * ≈ 50 K. The magnetic specific heat can be well fitted using a spinfluctuation model at low temperatures, yielding a large Sommerfeld coefficient, γ ≈ 172 mJ/mol K 2 at 6 K, suggesting that this is a heavy-fermion compound with a pronounced coherence effect. The magnetic susceptibility exhibits a broad field-independent peak at Tχ and shows an obvious anisotropy within the bc plane, reflecting the anisotropy of the coherence effect at high temperatures.These are compared with strongly correlated calculations combining first-principles band structure calculations and dynamical mean-field theory. Our results confirm the onset of coherence at about 50 K and reveal a similar anisotropy in the hybridization gap, pointing to a close connection between the hybridization strength of the low-temperature Fermi-liquid state and the high-temperature coherence effect. FIG. 1: (Color online) (a) Picture of the CeCoInGa3 single crystal of the size of about 0.5 mm × 0.3 mm × 2.5 mm. (b) The orthorhombic unit cell of CeCoInGa3 (space group Cmcm, No. 63). (c) The representation of multiple unit cells. The zone circled by the dashed line is enlarged with the lattice planes indexed as in (a).

A new oxide, LaMn3Ni2Mn2O12, was prepared by high-pressure and high-temperature synthesis methods. The compound crystallizes in an AA′3B2B′2O12-type A-site and B-site ordered quadruple perovskite structure. The charge combination is confirmed to be LaMn3+ 3Ni2+ 2Mn4+ 2O12, where La and Mn3+ are 1:3 ordered at the A and A′ sites and the Ni2+ and Mn4+ are also distributed at the B and B′ sites in an orderly fashion in a rocksalt-type manner, respectively. A G-type antiferromagnetic ordering originating from the A′-site Mn3+ sublattice is found to occur at T N ≈ 46 K. Subsequently, the spin coupling between the B-site Ni2+ and B′-site Mn4+ sublattices leads to an orthogonally ordered spin alignment with a net ferromagnetic component near T C ≈ 34 K. First-principles calculations demonstrate that the A′-site Mn3+ spins play a crucial role in determining the spin structure of the B and B′ sites. This LaMn3Ni2Mn2O12 provides a rare example that shows orthogonal spin ordering in the B and B′ sites assisted by ordered A-site magnetic ions in perovskite systems.

We revisited the anisotropy of the heavy-fermion material CeCo2Ga8 by measuring the electrical resistivity and magnetic susceptibility along all the principal a-, b-and c-axes. Resistivity along c-axis (ρc) shows clear Kondo coherence below about 17 K, while both ρa and ρ b remain incoherent down to 2 K. The magnetic anisotropy is well understood within the theoretical frame of crystalline electric field effect in combination with magnetic exchange interactions. We found the anisotropy ratio of these magnetic exchange interactions, |J c ex /J a,b ex |, reaches a large value of 4-5. We, therefore, firmly demonstrate that CeCo2Ga8 is a quasi-one-dimensional heavy-fermion compound both electrically and magnetically, and thus provide a realistic example of Kondo chain.

Understanding natural flows in porous media with low Reynolds number (Re) has significant implications for both science and engineering. However, knowledge and experimental gaps remain regarding such natural flows. In this context, we designed a sand column-based laboratory filtration experiment to investigate flow characteristics in porous media with low Re. Four media were considered including two silts (silt-I and silt-II), one silty sand, and one medium sand. Results show that constant hydraulic head is presumed to be an important factor that affects flow regime in porous media. In general, the flow approaches Darcian at a constant hydraulic head of ~170 cm, whereas it becomes non-Darcian at a constant hydraulic head of ~230 cm. The type of media determines the Re range that delimitates between Darcy and non-Darcy flows. Specifically, the transition appears at 0.015 < Re < 0.020 for medium sand and 0.000027 < Re < 0.000029 for silt-II, respectively. In the condition of constant hydraulic heads, the breakdown of Darcy’s law may occur at very low Re values (Re→0). Media dependent Re ranges are probably needed to describe the beginning of non-Darcy flows, rather than 1 to 10 or other value for all media. Findings in this study can offer insights into calculation and simulation of flows in low-permeability reservoirs, pumping process of foundation pit excavation, and other non-Darcy flows in low-permeability media.

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