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We report a local probe investigation of the frustrated antiferromagnet ${\mathrm{Pr}}_{3}{\mathrm{BWO}}_{9}$ with a distorted kagome lattice. The absence of magnetic order or spin-freezing is indicated by a spectral analysis down to 0.3 K and by specific heat measurements down to 0.09 K. The Knight shifts show an upturn behavior with the sample cooling down, which is further suppressed by the external field. For the spin dynamics, gapped spin excitation is observed from the temperature dependence of spin-lattice relaxation rates, with the gap size proportional to the applied magnetic field intensity. Comparatively, an unexpected sharp peak is observed in the nuclear spin-spin relaxation rate data at ${T}^{*}\ensuremath{\sim}4\text{--}5$ K. These results indicate an unconventional persistent fluctuating paramagnetic ground state with antiferromagnetic collective spin excitations in the strongly frustrated spin system.

We present a $^{125}$Te nuclear magnetic resonance (NMR) study in the three-dimensional spin web lattice Cu$_3$TeO$_6$, which harbors topological magnons. The $^{125}$Te NMR spectra and the Knight shift $\mathcal{K}$ as a function of temperature show a drastic change at $T_\text{S}\sim 40$ K much lower than the Neel ordering temperature $T_\text{N}\sim 61$ K, providing evidence for the first-order structural phase transition within the magnetically ordered state. Most remarkably, the temperature dependence of the spin-lattice relaxation rate $T_1^{-1}$ unravels spin-gap-like magnetic excitations, which sharply sets in at $T^*\sim 75$ K, the temperature well above $T_\text{N}$. The spin gap behavior may be understood by weakly dispersive optical magnon branches of high-energy spin excitations originating from the unique corner-sharing Cu hexagon spin-1/2 network with low coordination number.

Spin-exchange relaxation-free atomic spin gyroscope (SERF gyro) has ultrahigh theoretical sensitivity and is regarded as one of the most potential atomic gyroscopes. To investigate its rotation response, a high linear atomic spin precession detection module was developed firstly by modifying the fiber reflective Sagnac interferometer for atomic spin precession detection and operating it in closed-loop mode. The SERF gyro based on K-Rb-21Ne comagnetometer was built and tested and appeared obvious nonlinear response feature. The nonlinear rotation response model was deduced by assuming the rotation-induced nuclei spin procession detecting as an in-situ magnetometer inside the SERF gyro and the fitting curves are in good agreement with the experimental results. The optimized pump power for maximum sensitivity and measurable dynamic range were analyzed theoretically and demonstrated experimentally. The investigation results show that the nonlinear rotation response is an intrinsic property of SERF gyro and its measurable dynamic range is limited due to the saturation characteristic of the sum of pumping and relaxation rate. This indicates that SERF gyro is propitious to a position gyroscope with high sensitivity.

We analyze the combined effects of hydrodynamic fluctuations and chiral magnetic effect (CME) for a chiral medium in the presence of a background magnetic field. Based on the recently developed non-equilibrium effective field theory, we show fluctuations give rise to a CME-related positive contribution to magnetoresistance, while the early studies without accounting for the fluctuations find a CME-related negative magnetoresistance. At zero axial relaxation rate, the fluctuations contribute to the transverse conductivity in addition to the longitudinal one., 31 pages, 3 figures, published version

We show that magnetic fluctuations can destroy the Hebel-Slichter peak in conventional superconductors. The Hebel-Slichter peak has previously been expected to survive even in the presence of strong electronic interactions. However, we show that antiferromagnetic fluctuations suppress the peak at q=0 in the imaginary part of the magnetic susceptibility χ′′+−(q,ω), which causes the Hebel-Slichter peak. This is of general interest as in many materials superconductivity is found near a magnetically ordered phase, and the absence of a Hebel-Slichter peak is taken as evidence of unconventional superconductivity in these systems. For example, no Hebel-Slichter peak is observed in the κ−(BEDT−TTF)2X organic superconductors but heat capacity measurements have been taken to indicate s-wave superconductivity. Similarly, experiments indicate nodeless superconductivity in many iron pnictide superconductors which exhibit no peak in the relaxation rate. If antiferromagnetic fluctuations destroy the putative Hebel-Slichter peak in organic superconductors, then the peak should be restored by applying a pressure, which is known to suppress antiferromagnetic correlations in these materials.

We present a microscopic study of a doped quantum spin liquid candidate, the hyperkagome ${\mathrm{Na}}_{3}{\mathrm{Ir}}_{3}{\mathrm{O}}_{8}$ compound, by using $^{23}\mathrm{Na}$ NMR. We determine the intrinsic behavior of the uniform q = 0 susceptibility via shift measurements and the dynamical response by probing the spin-lattice relaxation rate. Throughout the studied temperature range, the susceptibility is consistent with a semimetal behavior, though with electronic bands substantially modified by correlations. Remarkably, the antiferromagnetic fluctuations present in the insulating parent compound ${\mathrm{Na}}_{4}{\mathrm{Ir}}_{3}{\mathrm{O}}_{8}$ survive in the studied compound. The spin dynamics are consistent with ${120}^{\ensuremath{\circ}}$ excitation modes displaying short-range correlations.

Momentum-conserving quasiparticle collisions in two-dimensional Fermi gases give rise to a large family of exceptionally long-lived excitation modes. The lifetimes of these modes exceed by a factor $(T_F/T)^2\gg 1$ the conventional Landau Fermi-liquid lifetimes $\tau\sim T_F/T^2$. The long-lived modes have a distinct angular structure, taking the form of $\cos m\theta$ and $\sin m\theta$ with odd $m$ values for a circular Fermi surface, with relaxation rate dependence on $m$ of the form $m^4\log m$, valid at not-too-large $m$. In contrast, the even-$m$ harmonics feature conventional lifetimes with a weak $m$ dependence. The long-time dynamics, governed by the long-lived modes, takes the form of angular (super)diffusion over the Fermi surface. Altogether, this leads to unusual long-time memory effects, defining an intriguing transport regime that lies between the conventional ballistic and hydrodynamic regimes., Comment: 29 pgs, 6 fgs

Nuclear quadrupole resonance (NQR) measurements were performed on the heavy-fermion superconductor ${\mathrm{Ce}}_{3}{\mathrm{PtIn}}_{11}$ with ${T}_{\mathrm{c}}=0.32\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The temperature dependence of both spin-lattice relaxation rate $1/{T}_{1}$ and NQR spectra evidences the occurrence of two successive magnetic transitions with ${T}_{\mathrm{N}1}\ensuremath{\simeq}2.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{N}2}\ensuremath{\simeq}2.0\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. In successive magnetic transitions, even though the magnetic moment at the Ce(2) site plays a major role, the magnetic moment at the Ce(1) site also contributes to some extent. While a commensurate antiferromagnetic ordered state appears for ${T}_{\mathrm{N}2}lTl{T}_{\mathrm{N}1}$, a partially incommensurate antiferromagnetic ordered state is suggested for $Tl{T}_{\mathrm{N}2}$.

We performed $^{13}\mathrm{C}$-NMR measurements on an organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ to investigate the superconducting (SC) gap symmetry, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. As the temperature approaches 0 K, the Knight shift in the SC state decreases; the nuclear spin-lattice relaxation rate $1/{T}_{1}$ shows cubic temperature dependence below the SC transition temperature ${T}_{c}$ without a coherence peak. These results can be understood in terms of $d$-wave superconductivity. Moreover, an increase in $1/{T}_{1}T$ at lower temperatures was observed just above ${T}_{c}$; this behavior can be interpreted as an effect of spin-density-wave (SDW) fluctuation. We suggest that the $d$-wave superconductivity of $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ originates from SDW fluctuation.

Fluxonium qubits employ a chain of $N$ Josephson junctions in series. We investigate how the charge-noise induced coherence time ${T}_{2}$ of the qubit depends upon $N$, holding fixed the chain's effective capacitance and inductance. The pure dephasing rate decreases with $N$, but the relaxation rate increases. As a result, ${T}_{2}$ achieves a maximum. The optimal $N$ can be much smaller than the number typically chosen in experiments, implying that fluxonium qubits can be significantly simplified without compromising performance.

$^{7}\mathrm{Li}$ nuclear magnetic resonance and terahertz (THz) spectroscopies are used to probe magnetic excitations and their field dependence in the hyperhoneycomb Kitaev magnet $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$. Spin-lattice relaxation rate ($1/{T}_{1}$) measured down to 100 mK indicates the gapless nature of the excitations at low fields (below ${H}_{c}\ensuremath{\simeq}2.8$ T), in contrast to the gapped magnon excitations found in the honeycomb Kitaev magnet $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$ at zero applied magnetic field. At higher temperatures in $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}, 1/{T}_{1}$ passes through a broad maximum without any clear anomaly at the N\'eel temperature ${T}_{N}\ensuremath{\simeq}38$ K, suggesting the abundance of low-energy excitations that are indeed observed as two peaks in the THz spectra; both correspond to zone-center magnon excitations. At higher fields (above ${H}_{c}$), an excitation gap opens, and a redistribution of the THz spectral weight is observed without any indication of an excitation continuum, in contrast to $\ensuremath{\alpha}\ensuremath{-}{\mathrm{RuCl}}_{3}$ where an excitation continuum was reported.

We have performed magnetic susceptibility $(\ensuremath{\chi})$, heat capacity $({C}_{p})$, and nuclear magnetic resonance (NMR) measurements on the layered compound ${\mathrm{Na}}_{2}{\mathrm{Mn}}_{3}{\mathrm{O}}_{7}$ in which the magnetic ${\mathrm{Mn}}^{4+}$ ions constitute a maple-leaf lattice. At high temperature, $\ensuremath{\chi}$ follows the Curie-Weiss (CW) law with CW temperature as high as 152 K and ${\mathrm{Mn}}^{4+}$ ions are found to be in the high-spin state $(S=\frac{3}{2})$. With decreasing temperature, $\ensuremath{\chi}$ passes through a broad maximum at 115 K and decreases rapidly at low temperature. A similar broad peak appears at around 62 K in the magnetic contribution to heat capacity $({C}_{m})$. The temperature dependence of $\ensuremath{\chi}$ and ${C}_{m}$ are the characteristics of an one-dimensional Heisenberg antiferromagnetic spin chain with a nonmagnetic ground state. The obtained values of spin-gap energy $({\mathrm{\ensuremath{\Delta}}}_{s})$ and nearest-neighbor antiferromagnetic exchange coupling $(J)$ are 28 and 27 K, respectively. There is no evidence of a long-range magnetic ordering down to 2 K in heat capacity data, in agreement with spin-singlet ground state. These observations are further corroborated by $^{23}\mathrm{Na}$ NMR studies through measurements of both the NMR shift and the spin-lattice relaxation rate.

We investigate the relaxation rate of the RNdS black hole perturbed by neutral massless scalar field in the eikonal limit. We find that the fastest relaxation rate of the composed system increases with the cosmological constant for all spacetime dimensions. We also find that, when the cosmological constant decreases from maximum value to zero, the corresponding critical charge of the four-dimensional RNdS black hole maximizing the relaxation rate of the composed system gradually decreases monotonically to $\bar{Q}=0.726$. However, for the higher dimensional systems, this is not the case and the critical charges decrease from maximum to zero., 8 pages, to appear in PLB

We report the inverse Laplace transform analysis of the $^{139}\mathrm{La}$ nuclear spin-lattice relaxation rate $1/{T}_{1}$ (${\mathrm{ILTT}}_{1}$ analysis) in charge-ordered ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ (${T}_{\mathrm{charge}}\ensuremath{\simeq}80$ K, ${T}_{c}\ensuremath{\simeq}{T}_{\mathrm{spin}}^{\mathrm{neutron}}=30$ K), and shed light on its magnetic inhomogeneity. We deduce the probability density function $P(1/{T}_{1})$ of the distributed $1/{T}_{1}$ (i.e., the histogram of distributed $1/{T}_{1}$) by taking the inverse Laplace transform of the experimentally observed nuclear magnetization recovery curve $M(t)$. We demonstrate that spin freezing sets in in some domains precisely below the onset of charge order at ${T}_{\mathrm{charge}}$, but their volume fraction grows only gradually toward ${T}_{c}$. Nearly a half of the sample volume exhibits properties expected for canonical high-${T}_{c}$ cuprates without charge order even near ${T}_{c}$. Our findings explain why charge order does not suppress ${T}_{c}$ of ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ as significantly as in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}$.

We investigate the interplay between the lattice, charge, and spin dynamics in charge-ordered high ${T}_{c}$ cuprate ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}\phantom{\rule{4pt}{0ex}}({T}_{c}=4\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ based on the inverse Laplace transform (ILT) analysis of the $^{139}\mathrm{La}$ nuclear spin-lattice relaxation rate $1/{T}_{1}$ (dubbed ${\mathrm{ILTT}}_{1}$ analysis hereafter). A major thrust of the ${\mathrm{ILTT}}_{1}$ analysis is that one can deduce the probability density function $P(1/{T}_{1})$ of distributed $1/{T}_{1}$. We demonstrate that $1/{T}_{1}^{\text{lm}}$, defined as the log mean (i.e., the center of gravity on a logarithmic scale) of $P(1/{T}_{1})$, can be well approximated by $1/{T}_{1}^{\text{str}}$ deduced from the phenomenological stretched fit; however, $P(1/{T}_{1})$ can provide much richer insight into how the lattice, charge, and spin fluctuations and their distribution develop near and below the long-range charge order at ${T}_{\text{charge}}\ensuremath{\sim}54\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Upon entering the charge-ordered state, a divergent increase of $1/{T}_{1}^{\text{lm}}$ toward the spin ordering at ${T}_{\text{spin}}^{\ensuremath{\mu}\text{SR}}\ensuremath{\simeq}35\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ is accompanied by an asymmetric broadening of $P(1/{T}_{1})$. Even deep inside the charge-ordered state, $1/{T}_{1}$ at a gradually diminishing fraction of $^{139}\mathrm{La}$ sites continues to slow down as temperature is lowered, as expected for canonical superconducting ${\mathrm{CuO}}_{2}$ planes without enhanced spin fluctuations. The fraction of such canonical $^{139}\mathrm{La}$ sites almost disappears by $\ensuremath{\simeq}40\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. In contrast, nearly half of the $^{139}\mathrm{La}$ sites in ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}\phantom{\rule{4pt}{0ex}}({T}_{\text{charge}}\ensuremath{\simeq}80\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ still exhibit the canonical behavior without enhanced spin fluctuations even near its ${T}_{c}=31\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. These contrasting behaviors explain why superconductivity in ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}$ is more strongly suppressed than in ${\mathrm{La}}_{1.885}{\mathrm{Sr}}_{0.115}{\mathrm{CuO}}_{4}$ despite the lower onset temperature of the charge order.

We have performed $^{13}\mathrm{C}$ NMR measurements on $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BEDT}\ensuremath{-}\mathrm{STF})}_{2}{\mathrm{FeCl}}_{4}$ to reveal the mechanism of unconventional paramagneticlike behavior observed in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ systems. $^{13}\mathrm{C}$ NMR spectra and nuclear spin-lattice relaxation rate $1/{T}_{1}$ revealed that the $\ensuremath{\pi}$ and $3d$ electron systems undergo an antiferromagnetic transition simultaneously at 16 K with the assistance of the $\ensuremath{\pi}\ensuremath{-}d$ interaction. We found that the sublattice magnetizations of the $\ensuremath{\pi}$ and $3d$ spins show different temperature dependence below ${T}_{\mathrm{N}}$, which is derived from the magnetic coupling between the two sublattice systems with different magnetic natures. We discuss the relationship between the two different magnetization processes and the unconventional magnetic behavior in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ system.

By using mostly the muon-spin rotation/relaxation ($\ensuremath{\mu}\mathrm{SR}$) technique, we investigate the superconductivity (SC) of ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ ($x=0$ and 1.6) alloys, with ${T}_{c}=10.5$ and 9.1 K, respectively. At a macroscopic level, their superconductivity was studied by electrical resistivity, magnetization, and specific-heat measurements. In both compounds, the electronic specific heat and the low-temperature superfluid density data suggest a nodeless SC. The superconducting gap value and the specific heat discontinuity at ${T}_{c}$ are larger than that expected from BCS theory in the weak-coupling regime, indicating strong-coupling superconductivity in the ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ family. In ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3}\mathrm{O}$, multigap SC is evidenced by the field dependence of the electronic specific heat coefficient and the superconducting Gaussian relaxation rate, as well as by the temperature dependence of the upper critical field. Pt substitution suppresses one of the gaps, and ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{1.4}{\mathrm{Pt}}_{1.6}\mathrm{O}$ becomes a single-gap superconductor. By combining our extensive experimental results, we provide evidence for a multiple- to single-gap SC crossover in the ${\mathrm{Nb}}_{5}{\mathrm{Ir}}_{3\ensuremath{-}x}{\mathrm{Pt}}_{x}\mathrm{O}$ family.

We scrutinize the magnetic properties of $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl through its first-order metal-insulator transition at $T_{\rm CO}=30$ K by means of $^1$H nuclear magnetic resonance (NMR). While in the metal we find Fermi-liquid behavior with temperature-independent $(T_1T)^{-1}$, the relaxation rate exhibits a pronounced enhancement when charge order sets in. The NMR spectra remain unchanged through the transition and no magnetic order stabilizes down to 25 mK. Similar to the isostructural spin-liquid candidates $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ and $\kappa$-(BEDT-TTF)$_2$Ag$_2$(CN)$_3$, $T_1^{-1}$ acquires a dominant maximum (here around 5 K). Field-dependent experiments identify the low-temperature feature as a dynamic inhomogeneity contribution that is typically dominant over the intrinsic relaxation but gets suppressed with magnetic field., Comment: 6 pages, 4 figures; Supplemental Material: 3 pages, 2 figures, 1 table

We characterize spin-wave propagation and its modification by an electrical current in permalloy($\mathrm{Py}$)/$\mathrm{Pt}$ bilayers with $\mathrm{Py}$ thickness between 4 and 20 nm. First, we analyze the frequency nonreciprocity of surface spin waves and extract from it the interfacial Dzyaloshinskii-Moriya interaction constant ${D}_{s}$ accounting for an additional contribution due to asymmetric surface anisotropies. Second, we measure the spin-wave relaxation rate and deduce from it the $\mathrm{Py}$/$\mathrm{Pt}$ spin-mixing conductance ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}$. Last, applying a dc electrical current, we extract the spin Hall conductivity ${\ensuremath{\sigma}}_{\mathrm{SH}}$ from the change of spin-wave relaxation rate due to the spin Hall spin-transfer torque. We obtain a consistent picture of the spin-wave propagation data for different film thicknesses using a single set of parameters ${D}_{s}=0.25$ pJ/m, ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}=3.2\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$ and ${\ensuremath{\sigma}}_{\mathrm{SH}}=4\ifmmode\times\else\texttimes\fi{}{10}^{5}$ S/m.

We consider the simplest model for $T$ - linear growth of resistivity in metals. It is shown that the so called "Planckian" limit for the temperature dependent relaxation rate of electrons follows from a certain procedure for representation of experimental data on resistivity and, in this sense, is a kind of delusion., 5 pages, 1 figure

Creating a transmon qubit using semiconductor-superconductor hybrid materials not only provides electrostatic control of the qubit frequency, it also allows parts of the circuit to be electrically connected and disconnected in situ by operating a semiconductor region of the device as a field-effect transistor. Here, we exploit this feature to compare in the same device characteristics of the qubit, such as frequency and relaxation time, with related transport properties such as critical supercurrent and normal-state resistance. Gradually opening the field-effect transistor to the monitoring circuit allows the influence of weak-to-strong dc monitoring of a "live" qubit to be measured. A model of this influence yields excellent agreement with experiment, demonstrating a relaxation rate mediated by a gate-controlled environmental coupling.

It is widely known that spin-locking noise-spectroscopy is a powerful technique for the characterization of low-frequency noise mechanisms in superconducting qubits. Here we show that the relaxation rate of the driven spin-locking state of a qubit can be significantly affected by the presence of an off-resonant high-frequency two-level-system defect. Thus, both low- and high-frequency defects should be taken into account in the interpretation of spin-locking measurements and other types of driven-state noise-spectroscopy., Comment: main text (6 pages, 3 figures) + supplemental material (8 pages, 9 figures)

We report a $^{35}$Cl nuclear magnetic resonance (NMR) study of the diluted Kitaev material $\alpha$-Ru$_{1-x}$Ir$_x$Cl$_3$ ($x=0.1$ and $0.2$) where non-magnetic Ir$^{3+}$ dopants substitute Ru$^{3+}$ ions. Upon dilution, the $^{35}$Cl spectra exhibit unusual large magnetic inhomogeneity, which sets in at temperatures below the Kitaev exchange energy scale. At the same time, the $^{35}$Cl spin-lattice relaxation rate $T_1^{-1}$ as a function of dilution and magnetic field unravels a critical doping of $x_c\approx 0.22$, towards which both the field-induced spin gap and the zero-field magnetic ordering are simultaneously suppressed, while novel gapless low-energy spin excitations dominate the relaxation process. These NMR findings point to the stabilization of a random singlet phase in $\alpha$-Ru$_{1-x}$Ir$_x$Cl$_3$, arising from the interplay of dilution and exchange frustration in the quantum limit., Comment: 5 pages, 2 figures, Publilished in PRB

The thermal conductivity of a trapped dipolar Bose condensed gas is calculated as a function of temperature in the framework of linear response theory. The contributions of the interactions between condensed and noncondensed atoms and between noncondensed atoms in the presence of both contact and dipole-dipole interactions are taken into account to the thermal relaxation time, by evaluating the self-energies of the system in the Beliaev approximation. We will show that above the Bose-Einstein condensation temperature (T > T BEC ) in the absence of dipole-dipole interaction, the temperature dependence of the thermal conductivity reduces to that of an ideal Bose gas. In a trapped Bose-condensed gas for temperature interval k B T <> k B T, since the relaxation rate $$ {\tau}_{c12}^{-1} $$ is independent of temperature and the relaxation rate due to dipolar interaction goes to zero exponentially, the T 2 temperature behavior for the thermal conductivity comes from the thermal mean velocity of the particles. We will also show that in the high-temperature limit (k B T > n 0 g B ) and low momenta, the relaxation rates $$ {\tau}_{c12}^{-1} $$ and $$ {\tau}_{dd12}^{-1} $$ change linearly with temperature for both dipolar and contact interactions and the thermal conductivity scales linearly with temperature.

We report on investigations of nonlinear magneto-optical rotation (NMOR) in rubidium vapor subjected to a modulated magnetic field and continuous-wave (CW) laser-light illumination. By superimposing modulation and a static (DC) magnetic field, we demonstrate the appearance of resonances at both small and large (compared to the ground-state relaxation rate) values of the static field. Since in conventional NMOR, there is no rotation at high fields, this suggests an existence of a novel mechanism generating anisotropy in the considered case, which we identify as parametric resonance. The experiments are performed using light of small ellipticity and rotation signals are significantly enhanced by combining atom-induced polarization rotation with a passive rotation induced with a wave plate. All the observations are supported with theoretical simulations. The density-matrix formalism and angular-momentum probability surfaces are used to provide intuitive explanation of the observed signals., 10 pages, 11 figures

$^{51}\mathrm{V}$ nuclear magnetic resonance (NMR) and magnetization studies on ${\mathrm{CeTi}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}{\mathrm{Ge}}_{3}$ have been performed to explore the evolution from the ferromagnetic ($x=0.113$) to the antiferromagnetic Kondo lattice state ($x=1$), with focus on the emergence of a possible ferromagnetic quantum critical point (FMQCP) at ${x}_{c}\ensuremath{\approx}0.4$. From the temperature dependence of the nuclear spin-lattice relaxation rate, $1/{T}_{1}T$, and the Knight shift, $K$, for $x=0.113$ and $x=1$ a considerable competition between ferro- and antiferromagnetic correlations is found. Around the critical concentration ($x=0.35,0.405$), quantum-critical spin fluctuations entail weak antiferromagnetic spin fluctuations admixed with ferromagnetic spin fluctuations. The FMQCP in ${\mathrm{CeTi}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}{\mathrm{Ge}}_{3}$ therefore is not purely ferromagnetic in nature.

To identify the key parameter for optimal superconductivity in iron pnictides, we measured the $^{31}\mathrm{P}$-NMR relaxation rate on ${\mathrm{BaFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}\phantom{\rule{4pt}{0ex}}(x=0.22$ and 0.28) under pressure and compared the effects of chemical substitution and physical pressure. For $x=0.22$, structural and antiferromagnetic (AFM) transition temperatures both show minimal changes with pressure up to 2.4 GPa, whereas the superconducting transition temperature ${T}_{\mathrm{c}}$ increases to twice its former value. In contrast, for $x=0.28$ near the AFM quantum critical point (QCP), the structural phase transition is quickly suppressed by pressure and ${T}_{\mathrm{c}}$ reaches a maximum. The analysis of the temperature-dependent nuclear relaxation rate indicates that these contrasting behaviors can be quantitatively explained by a single curve of the ${T}_{\mathrm{c}}$ dome as a function of Weiss temperature $\ensuremath{\theta}$, which measures the distance to the QCP. Moreover, the ${T}_{\mathrm{c}}\text{\ensuremath{-}}\ensuremath{\theta}$ curve under pressure precisely coincides with that with a chemical substitution, which is indicative of the existence of a universal relationship between low-energy AFM fluctuations and superconductivity on ${\mathrm{BaFe}}_{2}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{2}$.

We directly observe the hydrodynamic linear response of a unitary Fermi gas confined in a box potential and subject to a spatially periodic optical potential that is translated into the cloud at speeds ranging from subsonic to supersonic. We show that the time-dependent change of the density profile is sensitive to the thermal conductivity, which controls the relaxation rate of the temperature gradients and hence the responses arising from adiabatic and isothermal compression., 12 pages, 7 figures

We report 125Te-NMR studies on a newly discovered heavy fermion superconductor UTe2. Using a single crystal, we have measured the 125Te-NMR Knight shift K and spin-lattice relaxation rate 1/T1 for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static (K) and dynamical susceptibilities (1/T1) in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate 1/T2, when the field is applied along the easy axis of magnetization (=a axis). This behavior suggests the development of longitudinal magnetic fluctuations along the a axis at very low frequencies below 20 K., 5 pages, 7 figures, accepted for publication in J. Phys. Soc. Jpn

We have performed 31P-NMR measurements on the s-wave superconductor LaRu4P12 to investigate the magnetic field effect of the nuclear spin-lattice relaxation rate 1/T1 on a conventional full-gap superconductor. With increasing magnetic field, the Hebel-Slichter peak immediately below Tc in 1=T1 was suppressed, and the magnetic field dependence of 1/T1 at 0.8 K, well below Tc, was proportional to H2. These behaviors can be fully understood by the orbital pair-breaking effect in a single-band s-wave superconductor, 7pages, 4figures

We consider the isotropic $S=1$ Heisenberg chain with a finite Haldane gap $\Delta$ and use state-of-the-art numerical techniques to investigate its dynamical properties at finite temperature, focusing on the nuclear spin-lattice relaxation rate $1/T_1$ measured in nuclear magnetic resonance (NMR) experiments for instance. In particular, we analyze the contributions from modes with momenta close to $q\approx 0$ and $q\approx \pi$ as a function of temperature. At high-temperature, we observe spin diffusion with a non-trivial exponent. At low-temperature, we argue that a simple activated behavior $1/T_1 \propto\exp(-\Delta/T)$ can only be observed at temperatures much smaller than the gap $\Delta$., Comment: published version

We compute the spontaneous relaxation rate of a two-level atom in a planar cavity with parity ($\mathcal{P}$) and parity-time ($\mathcal{PT}$) symmetry. We find that at the center of a $\mathcal{PT}$-symmetric cavity the evanescent contribution to the relaxation rate is greatly suppressed. As this is the dominant relaxation pathway for cavities smaller than the transition wavelength, $\mathcal{PT}$-symmetric microcavities are able to suppress the spontaneous relaxation rate dramatically and, in some cases, reduce it to below the free-space level. The ability to reduce the relaxation rate and lengthen the excited-state lifetime has many applications in quantum control and can, for example, be used to increase atomic trapping times, improve photonic storage, and help maintain the coherence of atomic qubits.

Kitaev's honeycomb spin-liquid model and its proposed realization in materials such as $\alpha$-RuCl$_3$, Li$_2$IrO$_3$ and Na$_2$IrO$_3$ continue to present open questions about how the dynamics of a spin-liquid are modified in the presence of non-Kitaev interactions as well as the presence of inhomogeneities. Here we use $^{23}$Na nuclear magnetic resonance to probe both static and dynamical magnetic properties in single crystal Na$_2$IrO$_3$. We find that the NMR shift follows the bulk susceptibility above 30 K but deviates from it below; moreover below $T_N$ the spectra show a broad distribution of internal magnetic fields. Both of these results provide evidence for inequivalent magnetic sites at low temperature, suggesting inhomogeneities are important for the magnetism. The spin-lattice relaxation rate is isotropic and diverges at $T_N$, suggesting that the Kitaev cubic axes may control the critical quantum spin fluctuations. In the ordered state, we observe gapless excitations, which may arise from site substitution, emergent defects from milder disorder, or possibly be associated with nearby quantum paramagnetic states distinct from the Kitaev spin liquid., Comment: To appear in PRB as Rapid Communication

A relaxation-rate formula is presented for the entropic lattice Boltzmann model (ELBM) — a discrete kinetic theory for hydrodynamics. The simple formula not only guarantees the discrete time H-theorem but also gives full consideration to the consistency with hydrodynamics. The relaxation rate calculated with the formula effectively characterizes the drastic changes of the flow fields. By using this formula, the computational cost of the ELBM is significantly reduced and the model now can be efficiently used for a broad range of applications including high Reynolds number flows.

We have studied modification of the fluorescence spectra of a room-temperature atomic rubidium vapor in the region of 85 R b and 87 R b D 2 lines while changing the temporal rate of linear (triangular) scanning of laser radiation frequency. An increase in the ramping speed over a certain value ( ≈ 10 6 M H z / s ) results in essential modification of magnitudes of individual atomic transitions, different on rising and falling slopes, which characterize transition from a steady-state interaction regime to a transient one. Our experimental results are very consistent with the developed theoretical model. The obtained results can be used for determination of atomic system parameters such as ground-state relaxation rate. Possible follow-up actions for the addressed control of atomic level population are discussed.

In this Rapid Communication, a set of $^{209}\mathrm{Bi}$-nuclear magnetic resonance (NMR)/nuclear quadrupole resonance (NQR) measurements has been performed to investigate the physical properties of superconducting (SC) ${\mathrm{BaTi}}_{2}{\mathrm{Bi}}_{2}\mathrm{O}$ from a microscopic point of view. The NMR and NQR spectra at 5 K can be reproduced with a nonzero in-plane anisotropic parameter $\ensuremath{\eta}$, indicating the breaking of the in-plane fourfold symmetry at the Bi site without any magnetic order, i.e., ``the electronic nematic state.'' In the SC state, the nuclear spin-lattice relaxation rate divided by temperature, $1/{T}_{1}T$, does not change even below ${T}_{\mathrm{c}}$, while a clear SC transition was observed with a diamagnetic signal. This observation can be attributed to the strong two dimensionality in ${\mathrm{BaTi}}_{2}{\mathrm{Bi}}_{2}\mathrm{O}$. Comparing the NMR/NQR results among ${\mathrm{BaTi}}_{2}P{n}_{2}\mathrm{O}$ ($Pn=\text{As}$, Sb, and Bi), it was found that the normal and SC properties of ${\mathrm{BaTi}}_{2}{\mathrm{Bi}}_{2}\mathrm{O}$ were considerably different from those of ${\mathrm{BaTi}}_{2}{\mathrm{Sb}}_{2}\mathrm{O}$ and ${\mathrm{BaTi}}_{2}{\mathrm{As}}_{2}\mathrm{O}$, which might explain the two-dome structure of ${T}_{\mathrm{c}}$ in this system.

In this paper, 133Cs nuclear magnetic resonance (NMR) measurements have been performed to investigate the magnetic properties of an A-type antiferromagnet CsCo 2 Se 2 . The field-sweeping NMR spectra become broadened mainly due to the internal magnetic field attributed to antiferromagnetic ordering. Both T -dependence of Knight shift 133 K and T divided spin-lattice relaxation rate 1/ T 1 T provide clear evidences for the antiferromagnetic transition at ∼ 70 K. 1/ T 1 T exhibits a Curie–Weiss T -dependence down to 80 K, suggesting the development of antiferromagnetic spin fluctuations with decreasing temperature. The linear-relationship between T 1 T - T suggests that antiferromagnetic spin fluctuations are two-dimensional in the paramagnetic state.

For a noncentrosymmetric superconductor such as Y2C3, we consider a parity-mixing model composed of spin-singlet s-wave and spin-triplet f-wave pairing components. The d-vector in f-wave state is chosen to be parallel to the Dresselhaus asymmetric spin-orbit coupling vector. It is found that, the quasiparticle excitation spectrum exhibits distinct nodal structure as a consequence of parity-mixing. We demonstrate particularly that such a model can qualitatively account for the existing experimental results of the temperature dependence of the nuclear spin-lattice relaxation rate T 1 − 1 in Y2C3.

We theoretically investigate the energy relaxation rate of magnons and phonons near the resonance points to clarify the underlying mechanism of heat transport in ferromagnetic materials. We find that the simple two-temperature model is valid for the one-phonon/one-magnon process, as the rate of energy exchange between magnons and phonons is proportional to the temperature difference between them, and it is independent of temperature in the high temperature limit. We found that the magnon-phonon relaxation time due to the one-phonon/one-magnon interaction could be reduced to 1.48 $\mu s$ at the resonance point by applying an external magnetic field. It means that the resonance effect plays a significant role in enhancing the total magnon-phonon energy exchange rate, apart from the higher order interaction processes.

We present $^{77}\mathrm{Se}$-NMR measurements on ${\mathrm{FeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ samples with sulfur content $x=0%$, 9%, 15%, and $29%$. Twinned nematic domains are observed in the NMR spectrum for all samples except $x=29%$. The NMR spin-lattice relaxation rate shows that antiferromagnetic (AFM) fluctuations are initially enhanced between $x=0%$ and $x=9%$, but are strongly suppressed for higher $x$ values. The observed behavior of the AFM fluctuations parallels the superconducting transition temperature ${T}_{\mathrm{c}}$ in these materials, providing strong evidence for the primary importance of AFM fluctuations for superconductivity, despite the presence of nematic quantum criticality in the ${\mathrm{FeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ system.

NMR captures mobile spin solitons deconfined from a charge-lattice–coupled nonmagnetic ferroelectric order., Topological defects have been explored in different fields ranging from condensed matter physics and particle physics to cosmology. In condensed matter, strong coupling between charge, spin, and lattice degrees of freedom brings about emergent excitations with topological characteristics at low energies. One-dimensional (1D) systems with degenerate dimerization patterns are typical stages for the generation of topological defects, dubbed “solitons”; for instance, charged solitons are responsible for high electrical conductivity in doped trans-polyacetylene. Here, we provide evidence based on a nuclear magnetic resonance (NMR) study for mobile spin solitons deconfined from a strongly charge-lattice–coupled spin-singlet ferroelectric order in a quasi-1D organic charge-transfer complex. The NMR spectral shift and relaxation rate associated with static and dynamic spin susceptibilities indicate that the ferroelectric order is violated by dilute solitonic spin excitations, which were further demonstrated to move diffusively by the frequency dependence of the relaxation rate. The traveling solitons revealed here may promise the emergence of anomalous electrical and thermal transport.

Recently observed 4{\pi} periodic Andreev bound states in three dimensional Dirac materials are attributed to convnetional superconducting pairing. Our alternative explanation in terms of a novel form of parity breaking pseudo-scalar superconducting order can be sharply diagnosed by nuclear magnetic resonance (NMR) relaxation rate. The left-right symmetry breaking of the pseudo-scalar superconductivity can be directly probed as an anti-peak structure below TC in sharp contrast to the conventional Hebel-Slichter peak.

Local NMR relaxation rates in the vortex state of chiral and helical $p$-wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate ${T}_{1}^{\ensuremath{-}1}$ and spin-spin relaxation rate ${T}_{2}^{\ensuremath{-}1}$. Depending on the relation between the NMR relaxation direction and the $d$-vector symmetry, the local ${T}_{1}^{\ensuremath{-}1}$ and ${T}_{2}^{\ensuremath{-}1}$ in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the $d$-vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency $s$-wave spin-triplet Cooper pairs. The difference between the local ${T}_{1}^{\ensuremath{-}1}$ and ${T}_{2}^{\ensuremath{-}1}$ in the site-selective NMR measurement is expected to be a method to examine the $d$-vector symmetry of candidate materials for spin-triplet superconductors.

The kappa-distributed fully ionized plasma with collisional interaction is investigated. The Fokker-Planck equation with Rosenbluth potential is employed to describe such a physical system. The results show that the kappa distribution is not a stationary distribution unless the parameter kappa tends to infinity. The general expressions of collisional relaxation rate of multiple-component plasma with kappa distribution are derived and discussed in specific cases in details. For the purpose of visual illustration, we also give those results numerically in figures. All the results show that the parameter kappa plays a significant role in relaxation rate.

The Kondo and Periodic Anderson Model (PAM) are known to provide a microscopic picture of many of the fundamental properties of heavy fermion materials and, more generally, a variety of strong correlation phenomena in $4f$ and $5f$ systems. In this paper, we apply the Determinant Quantum Monte Carlo (DQMC) method to include disorder in the PAM, specifically the removal of a fraction $x$ of the localized orbitals. We determine the evolution of the coherence temperature $T^*$, where the local moments and conduction electrons become entwined in a heavy fermion fluid, with $x$ and with the hybridization $V$ between localized and conduction orbitals. We recover several of the principal observed trends in $T^*$ of doped heavy fermions, and also show that, within this theoretical framework, the calculated Nuclear Magnetic Resonance (NMR) relaxation rate tracks the experimentally measured behavior in pure and doped CeCoIn$_5$. Our results contribute to important issues in the interpretation of local probes of disordered, strongly correlated systems., Comment: 8 pages, 4 figures