Heat transport can serve as a fingerprint identifying different states of matter. In normal liquid, hotspot diffuses, whereas in superfluid, heat propagates wave called "second sound." Direct imaging is challenging, and one usually resorts to detecting secondary effects. this study, we establish thermography strongly interacting atomic Fermi gas, whose radio-frequency spectrum provides spatially resolved thermometry with subnanokelvin resolution. The superfluid phase transition was directly...

We show that short-range pair correlations in a strongly interacting Fermi gas follow simple universal law described by Tan's relations. This is achieved through measurements of the static structure factor which displays scaling proportional to ratio contact momentum $C/q$. Bragg spectroscopy ultracold $^6$Li atoms from periodic optical potential used measure for wide range momenta and interaction strengths, providing broad confirmation this law. calibrate our spectra using $f$-sum rule,...

We present a comprehensive study of the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover in fermionic $^{6}\mathrm{Li}$ using Bragg spectroscopy. A smooth transition from molecular atomic spectra is observed with clear signature pairing at and above unitarity. These probe dynamic static structure factors gas provide direct link two-body correlations. have characterized these correlations measured their density dependence across broad Feshbach resonance 834 G.

We have studied the transition from two to three dimensions in a low temperature weakly interacting $^6$Li Fermi gas. Below critical atom number, $N_{2D}$, only lowest transverse vibrational state of highly anisotropic oblate trapping potential is occupied and gas two-dimensional. Above $N_{2D}$ enters quasi-2D regime where shell structure associated with filling individual oscillator states apparent. This dimensional crossover demonstrated through measurements cloud size aspect ratio versus number.

We present a high-precision determination of the universal contact parameter in strongly interacting Fermi gas. In trapped gas at unitarity, we find to be $3.06\ifmmode\pm\else\textpm\fi{}0.08$ temperature 0.08 harmonic trap. The governs high-momentum (short-range) properties these systems, and this low-temperature measurement provides new benchmark for zero-temperature homogeneous contact. experimental utilizes Bragg spectroscopy obtain dynamic static structure factors ultracold gases high...

Thermodynamic properties of matter are conveniently expressed as functional relations between variables known equations state. Here we experimentally determine the compressibility, density, and pressure state for an attractive 2D Fermi gas in normal phase a function temperature interaction strength. In 2D, interacting gases exhibit qualitatively different features to those found 3D. This is evident normalized density equation state, which peaks at intermediate densities corresponding...

We describe an experiment in which Bose-Einstein condensates and cold atom clouds are held by a microscopic magnetic trap near room-temperature metal wire 500 microm diameter. The lifetime for atoms to remain the microtrap is measured over range of distances down 27 from surface metal. observe loss due spin flips. These induced radio-frequency thermal fluctuations field surface, as predicted but not previously observed.

A versatile miniature de Broglie waveguide is formed by two parallel current-carrying wires in the presence of a uniform bias field. We derive variety analytical expressions to describe guide and present quantum theory show that it offers remarkable range possibilities for atom manipulation on submicron scale. These include controlled coherent splitting wave function as well cooling, trapping, guiding. In particular, we discuss novel microscopic interferometer with potential be exceedingly sensitive.

The contact ${\cal I}$, introduced by Tan, has emerged as a key parameter characterizing universal properties of strongly interacting Fermi gases. For ultracold gases near Feshbach resonance, the depends upon two quantities: interaction $1/(k_F a)$, where $k_F$ is wave-vector and $a$ $s$-wave scattering length, temperature $T/T_F$, $T_F$ temperature. We present first measurements dependence in unitary gas using Bragg spectroscopy. seen to follow predicted decay with shows how...

We present an experimental study of the high-energy excitation spectra unitary Fermi gases. Using focussed beam Bragg spectroscopy, we locally probe atoms in central region a harmonically trapped cloud where density is nearly uniform, enabling measurements dynamic structure factor for range temperatures both below and above superfluid transition. Applying sum-rules to measured spectra, resolve characteristic behaviour universal contact parameter, ${\cal C}$, across also employ recent...

We present measurements of the binding energies $^{6}\text{L}\text{i}$ $p$-wave Feshbach molecules formed in combinations $|F=1/2,{m}_{F}=+1/2⟩$ $(|1⟩)$ and $|F=1/2,{m}_{F}=\ensuremath{-}1/2⟩$ $(|2⟩)$ states. The scale linearly with magnetic field detuning for all three resonances. relative molecular moments are found to be $113\ifmmode\pm\else\textpm\fi{}7\text{ }\ensuremath{\mu}\text{K}/\text{G}$, $111\ifmmode\pm\else\textpm\fi{}6\text{ $118\ifmmode\pm\else\textpm\fi{}8\text{...

We present an experimental investigation of collective oscillations in harmonically trapped Fermi gases through the crossover from two to three dimensions. Specifically, we measure frequency radial monopole oscillation or breathing mode highly oblate with tunable interactions. The is set by adiabatic compressibility and probes thermodynamic equation state. In 2D, a dynamical scaling symmetry for atoms interacting via $\ensuremath{\delta}$ potential predicts occur at exactly twice harmonic...

Symmetry-breaking phase transitions are central to our understanding of states matter. When a continuous symmetry is spontaneously broken, new excitations appear that tied fluctuations the order parameter. In superconductors and fermionic superfluids, amplitude can fluctuate independently, giving rise two distinct collective branches. However, difficult both generate measure, as they do not couple directly density fermions have only been observed indirectly date. Here, we excite oscillations...

We model weak gravitational lensing of light by large-scale structure using ray tracing through N-body simulations. The method is described with particular attention paid to numerical convergence. investigate some the key approximations in multiplane ray-tracing algorithm. Our simulated shear and convergence maps are used explore how well standard assumptions about hold, especially near large peaks signal.

We present an experimental investigation of the dynamic spin response a strongly interacting Fermi gas using Bragg spectroscopy. By varying detuning lasers, we show that it is possible to measure in and density channels separately. At low energies, suppressed due pairing, whereas enhanced. These experiments yield first independent measurements spin-parallel spin-antiparallel static structure factors, which provide insight into different features functions. high momentum factor displays...

We present experiments with Bose-Einstein condensates on a combined atom chip. The structure consists of large-scale "carrier chip" and smaller "atom-optics chips", containing micron-sized elements. This allows us to work very close chip surfaces without suffering from fragmentation or losses due thermally driven spin flips. Precise three-dimensional positioning transport constant trap frequencies are described. were manipulated submicron accuracy above atom-optics chips. As an application...

We calculate and measure the density distribution cloud size of a trapped two-dimensional $^{6}$Li Fermi gas near Feshbach resonance at low temperatures. Density distributions sizes are calculated for wide range interaction parameters using local approximation (LDA) zero-temperature equation state obtained from quantum Monte Carlo simulations reported by G. Bertaina S. Giorgini, Phys. Rev. Lett. \textbf{106}, 110403 (2011). find that LDA predictions agree well with experimental measurements...

Upcoming Sunyaev-Zel'dovich surveys are expected to return ~10^4 intermediate mass clusters at high redshift. Their average masses must be known same accuracy as desired for the dark energy properties. Internal surveys, CMB potentially provides a source lensing measurements whose distance is precisely and behind all clusters. We develop statistical estimators from 6 quadratic combinations of temperature polarization fields that can simultaneously recover large-scale structure cluster...

We theoretically investigate superfluidity in a strongly interacting Fermi gas confined to two dimensions at finite temperature. Using Gaussian pair fluctuation theory the superfluid phase, we calculate density and determine critical temperature chemical potential Berezinskii-Kosterlitz-Thouless transition. propose that transition can be unambiguously demonstrated cold-atom experiments by stirring using red-detuned laser beam, identify characteristic jump local Landau velocity...

Ultracold Fermi gases subject to tight transverse confinement offer a highly controllable setting study the two-dimensional (2D) BCS Berezinskii-Kosterlitz-Thouless superfluid crossover. Achieving 2D regime requires confining particles their ground state which presents challenges in interacting systems. Here, we establish conditions for an gas display kinematics. Transverse excitations are detected by measuring expansion rate displays sudden increase when atom number exceeds critical value...

We present an experimental and theoretical study of the phonon mode in a unitary Fermi gas. Using two-photon Bragg spectroscopy, we measure excitation spectra at momentum approximately half momentum, both above below superfluid critical temperature $T_\mathrm{c}$. Below $T_\mathrm{c}$, dominant is Bogoliubov-Anderson (BA) mode, driven by gradients phase order parameter. The dependence BA consistent with model based on quasiparticle random approximation which damping mechanism via collisions...

We study the formation of a Bose-Einstein condensate in cigar-shaped three-dimensional harmonic trap, induced by controlled addition an attractive ``dimple'' potential along weak axis. In this manner we are able to induce condensation without cooling due localized increase phase-space density. perform quantitative analysis thermodynamic transformation both sudden and adiabatic regimes for range dimple widths depths. find good agreement with equilibrium calculations based on self-consistent...