This repository contains data accompanying the manuscript 

T.A. Hilker, L.H. Dogra, C. Eigen, J.A.P. Glidden, R.P. Smith, and Z. Hadzibabic.
“First and Second Sound in a Compressible 3D Bose Fluid”
Published in Physical Review Letters 128 223601 on June 2, 2022
Available: https://link.aps.org/doi/10.1103/PhysRevLett.128.223601

Any additional information is available from the corresponding authors upon reasonable request.

CONTENTS
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Files with the data of Figure 2
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Figure_2a: 
The measured center-of-mass velocities for given shaking time and shaking frequency.

Figure_2b: 
The optical conductivities are extracted from the amplitudes of the quasi steady-state oscillations in arbitrary units for given normalized temperatures and frequencies.

Figure_2c_exp: 
The speeds of sound from fitting the resonances of the optical conductivity for first and second sound. Reduced temperatures are based on measured temperatures and atom numbers using the relation for the non-interacting Tc in our trap. 

Figure_2c_th: 
The theoretical predictions for the speed of sound are based on our trap geometry and a range of atom numbers. Calculations are based on mean-field theory (see Supplemental Material of the paper) and are performed at a fixed temperature of 97 nK. 

Files with the data of Figure 3
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Figure_3ad: 
Two-dimensional table with the measured momentum space densities. The fourth row lists the shaking times t. The first column lists the shaking frequency [14 Hz (second sound), 40 Hz (first sound)] and the second column the wave vectors k.

Figure_3be:
Phases of the momentum-resolved response from fitting the time evolution of the experimental momentum space densities.

Figure_3cf:
Superfluid and normal velocity of the cloud from the momentum space densities (see Supplemental Material).

Files with the data of Figure 4
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Figure_4a: 
Center of mass velocity of the gas during free oscillations after exciting a wave for different interactions and excitation phases.

Figure_4bc_exp:
Speeds of sound and damping. The table gives the following quantities
L, calibrated box size
a, interactions calculated from the calibrated applied magnetic field
L/l_mfp,  corresponding inverse Knudsen number
temperature, measured from the wings of the distribution
c_I^HF, the expected speeds of sounds at each parameter set based on dissipationless Hartree Fock theory
c_I, speed of sound from fitting the free oscillations
gamma_I, damping from fitting the free oscillations.  

Figure_4bc_th:
Theoretical prediction (see Supplemental Material) for the dimensionless speed of sound and damping for a range of inverse Knudsen numbers. 
c_I_phi and gamma_I are the phase velocity and damping of the first sound based on the hydrodynamic theory without linearization of the transport terms. 
c_i is the speed of sound
c_II_ph and gamma_II are the phase velocity and damping of the second sound with the former being zero because we treat a classical gas. Given as additional information
gamma_I_SK, the Stokes-Kirchoff damping.