We performed AC calorimetry and magnetoresistance measurements under pressure for H || a-axis (easy-magnetization axis) in the novel heavy-fermion superconductor UTe2. Thanks to thermodynamic information, multiple superconducting phases have been revealed magnetic field. The (H,T) phase diagram of superconductivity displays an abrupt increase upper critical field (Hc2) at low temperature high region, a strong convex curvature Hc2 temperature. This behavior require state order parameter more...

We have performed the 125Te-nuclear magnetic resonance (NMR) measurement in field along b axis on newly discovered superconductor UTe2, which is a candidate of spin-triplet superconductor. The nuclear spin–lattice relaxation rate divided by temperature 1/T1T abruptly decreases below superconducting (SC) transition Tc without showing coherence peak, indicative UTe2 being an unconventional It was found that dependence SC state cannot be understood single gap behavior but can explained two...

We report 125Te-NMR studies on a newly discovered heavy fermion superconductor UTe2. Using single crystal, we have measured the Knight shift K and spin-lattice relaxation rate 1/T1 for fields along three orthorhombic crystal axes. The data confirm moderate Ising anisotropy both static (K) dynamical susceptibilities (1/T1) in paramagnetic state above about 20 K. Around K, however, observed sudden loss of NMR spin-echo signal due to enhancement spin-spin 1/T2, when field is applied easy axis...

We report the first observation of de Haas-van Alphen (dHvA) effect in novel spin-triplet superconductor UTe2 using high quality single crystals with residual resistivity ratio (RRR) over 200. The dHvA frequencies, named alpha and beta, are detected for field directions between c a-axes. frequency branch beta increases rapidly angle tilted from to a-axis, while splits, owing maximal minimal cross-sectional areas same Fermi surface. Both branches, reveal two kinds cylindrical surfaces a...

This study investigates the spin susceptibility in U-based superconductor UTe$_2$ superconducting (SC) state by using Knight shift measurements for a magnetic field $H$ along $a$ axis, which is easy axis of UTe$_2$. Although tiny anomaly ascribed to SC diamagnetic effect was observed just below transition temperature $T_{\rm c}$, $a$-axis shows no significant decrease, following extrapolation from normal-state dependence. indicates that nearly unchanged c}$. Considering previous results $H...

Spin susceptibility in the superconducting (SC) state was measured higher-quality sample of uranium-based superconductor UTe2 by using Knight-shift measurements for a magnetic field H along all three crystalline axes. In sample, SC transition temperature Tc is about 2.1 K, and residual electronic term specific heat almost zero. The NMR linewidth becomes narrower half that previous with ∼ 1.6 K when || c. Although behavior not so different from results b, c, large reduction Knight shift axis...

$\mathrm{U}{\mathrm{Te}}_{2}$ is a recently discovered spin-triplet superconductor. One of the characteristic features magnetic field ($H$)-boosted superconductivity >16 T when $H$ applied exactly parallel to $b$ axis. To date, this superconducting (SC) state has not been thoroughly investigated, and SC properties as well spin high-$H$ (HHSC) phase are understood. In letter, we performed AC susceptibility nuclear resonance measurements found that, up 24.8 T, HHSC bulk nature quite sensitive...

We grew single crystals of the recently discovered heavy fermion superconductor UTe2, and measured resistivity, specific heat magnetoresistance. Superconductivity (SC) was clearly detected at Tsc=1.65K as sharp drop resistivity in a high quality sample RRR=35. The shows large jump Tsc indicating strong coupling. Sommerfeld coefficient, 117mJ K-2mol-1 extrapolated normal state temperature dependence C/T below are signature unconventional SC. discrepancy entropy balance between SC states...

To investigate spin susceptibility in a superconducting (SC) state, we measured the $^{125}\mathrm{Te}$-NMR Knight shifts at magnetic fields ($H$) up to 6.5 T along $b$ and $c$ axes of single-crystal ${\mathrm{UTe}}_{2}$, promising candidate for spin-triplet superconductor. In SC (${K}_{b}$ ${K}_{c}$, respectively) decreased slightly, decrease ${K}_{b}$ was almost constant T. The reduction ${K}_{c}$ with increasing $H$, unchanged through transition temperature 5.5 T, excluding possibility...

We report the magnetic susceptibility and magnetization under pressures up to 1.7GPa above critical pressure, Pc ~ 1.5GPa, for H // a, b, c-axes in novel spin triplet superconductor UTe2. The anisotropic at low pressure with easy a-axis changes quasi-isotropic behavior high revealing a rapid suppression of a-axis, gradual increase b-axis. At Pc, anomalies are detected T_MO 3K T_WMO 10K. former anomaly corresponds long-range order, most likely antiferromagnetism, while latter shows broad...

125Te NMR experiments in field (H) applied along the easy magnetization axis (the a-axis) revealed slow electronic dynamics developing paramagnetic state of UTe2. The observed fluctuations are concerned with a successive growth long-range correlations below 30–40 K, where spin susceptibility hard b-axis) shows broad maximum. also imply that tiny amounts disorder or defects locally disturb and develop an inhomogeneous at low temperatures, leading to temperature upturn bulk-susceptibility H ||...

We studied the anisotropy of superconducting upper critical field $H_{\rm c2}$ in heavy-fermion superconductor UTe$_2$ under hydrostatic pressure by magnetoresistivity measurements. In agreement with previous experiments we confirm that superconductivity disappears near a $p_{\rm c} \approx 1.5$~GPa, and magnetically ordered state appears. The unusual c2}(T)$ at low temperatures for $H \parallel a$ suggests multiple phases which appear have quite different c2}$. For applied along hard...

This paper studies the field-angle dependencies of high-quality single crystal UTe${}_{2}$ in standard and superconductivity states. The results suggest presence point nodes along $a$ axis superconducting gap.

Superconducting (SC) state has spin and orbital degrees of freedom, spin-triplet superconductivity shows multiple SC phases due to the presence these freedom. However, observation spin-direction rotation occurring inside (SC rotation) hardly been reported. UTe2, a recently discovered topological superconductor, exhibits various under pressure: at ambient pressure (SC1), high-temperature above 0.5 GPa (SC2), low-temperature (SC3). We performed nuclear magnetic resonance AC susceptibility...

Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URu$_2$Si$_2$ were investigated by specific-heat $C(T, H, ϕ, θ)$ measurements of a high-quality single crystal. The occurrence QP due to Doppler-shift effect was detected regardless field direction $C(H)$ present clean sample, which is sharp contrast previous report. Furthermore, polar-angle-dependent $C(θ)$ measured under rotating magnetic within ac plane exhibits shoulder-like anomaly at $θ\sim 45$ deg and dip...

We report the magnetoresistance in novel spin-triplet superconductor UTe2 under pressure close to critical Pc, where superconducting phase terminates, for field along three a, b and c-axes orthorhombic structure. The H // a-axis just below Pc shows a field-reentrant behavior due competition with emergence of magnetic order at low fields. upper Hc2 c-axis quasi-vertical increase H-T diagram indicating that superconductivity is reinforced by strong fluctuations which persist even high fields...

Metamagnetic transitions in the novel spin-triplet superconductor UTe$_2$ were investigated through newly developed simultaneous measurements of magnetization and sample temperature for field along orthorhombic $b$-axis close to [011] direction, where reentrant superconductivity (RSC) is detected below above first-order metamagnetic transition $H_{\rm m}$. Combining Maxwell's relation Clausius-Clapeyron equation, we obtained dependence Sommerfeld coefficient $\gamma$ transition. A...

UTe$_2$ is a recently discovered promising candidate for spin-triplet superconductor. In contrast to conventional spin-singlet superconductivity, superconductivity possesses spin and angular momentum degrees of freedom. To detect these freedom obtain the solid evidence in UTe$_2$, we performed $^{125}$Te-NMR measurement. We previously reported that shoulder signal appears NMR spectra below superconducting (SC) transition temperature $T_{\rm c}$ $H \parallel b$, slight decrease Knight shift...

Low-energy quasiparticle excitations in the superconducting (SC) state of UBe_{13} were studied by means specific-heat (C) measurements a rotating field. Quite unexpectedly, magnetic-field dependence C(H) is linear H with no angular at low fields SC state, implying that gap fully open over Fermi surfaces, stark contrast to previous expectations. In addition, characteristic cubic anisotropy was observed above 2 T maximum (minimum) for H∥[001] ([111]) within (11[over ¯]0) plane, normal as well...

Resistivity measurements were performed for the itinerant Ising-type ferromagnet URhAl at temperatures down to 40 mK under high pressure up 7.5 GPa, using single crystals. We found that critical of Curie temperature exists around ${P}_{\mathrm{c}}\ensuremath{\sim}$ 5.2 GPa. Near ${P}_{\mathrm{c}}$, $A$ coefficient $A{T}^{2}$ Fermi-liquid resistivity term below ${T}^{*}$ is largely enhanced with a maximum 5.2--5.5 Above exponent $\ensuremath{\rho}(T)$ deviates from 2. At it close $n=5/3$,...

We have studied the magnetization of recently discovered heavy fermion superconductor UTe$_2$ up to 56 T in pulsed-magnetic fields. A first-order metamagnetic transition has been clearly observed at $H_{\rm m}$ =34.9 when magnetic field $H$ is applied along orthorhombic hard-magnetization $b$-axis. The a critical end point $\sim$11 K and 34.8 T, where first order terminates changes into crossover regime. Using thermodynamic Maxwell relation, we evaluated dependence Sommerfeld coefficient...

The link between the metamagnetic transition and novel spin-triplet superconductivity of UTe$_2$ was discussed thermodynamically through magnetostriction measurements in a pulsed-magnetic field. We revealed discontinuous across at $μ_0H_{\rm m}\approx 35$~T for applied magnetic fields along crystallographic $b$ axis orthorhombic structure. resultanting volume $ΔV/V \approx-5.9\times 10^{-4}$ gives initial pressure dependence $H_{\rm m}$ by employing Clausius-Clapeyron's equation, which...

The phase diagram of the quasi-2D Ce(Ir,Rh)In5 system contains two distinct superconducting domes. By thermal transport measurements in rotating magnetic fields H, we pinned down gap structure CeIrIn5 second dome, located distant from first dome proximity to an antiferromagnetic quantum critical point. Clear fourfold oscillation was observed when H is rotated within ab plane, while no bc plane. In sharp contrast previous reports, our results are most consistent with dx2-y2 symmetry, implying...