Absolute static-field magnetometry, magnetic gradiometry, and vector electrometry with circular Rydberg atoms

Helium atoms in pulsed supersonic beams have been prepared in the circular Rydberg state with principal quantum number n = 55 using the crossed-fields method. High-resolution microwave spectroscopy of the transition from this state to the n = 56 circular state, at frequencies close to 38.5 GHz, was performed to measure static magnetic and electric fields along the axis of propagation of the beams with quantum-state-selective detection by pulsed-electric-field ionization. Magnetic fields of between 1.3 and 1.6 mT were measured to a relative precision of ±900 nT by rf spectroscopy and ±1.3 µT by microwave spectroscopy, with absolute calibration, accounting for Doppler shifts and effects of weak stray electric fields to ±2.0 µT and a spatial resolution of ±0.87 mm. Magnetic-field gradients could be determined to a precision of ±1.49 µT/mm (±53 nT/mm) over a baseline of 1.74 mm (35 mm). To perform these measurements, static electric fields and contributions from the motional Stark effect were minimized, and residual electric fields in each of the three spatial dimensions in the apparatus were measured to an absolute precision of between ±85 and ±750 µV/cm. The methods used in this work can be transferred to experiments with other atoms or molecules. They are therefore well suited for applications in minimally invasive, absolute static-field magnetometry and electrometry, for example, at hybrid interfaces between Rydberg atoms and superconducting circuits; in tests of bound-state QED or the weak equivalence principle with atomic or molecular hydrogen, antihydrogen, or positronium; and in measurements of the absolute neutrino mass by cyclotron radiation emission spectroscopy

Doping driven structural distortion in the bilayer iridate (Sr1−x_{1-x}Lax_x)3_3Ir2_2O7_7

Neutron single crystal diffraction and rotational anisotropy optical second harmonic generation data are presented resolving the nature of the structural distortion realized in electron-doped (Sr$_{1-x}$La$_x$)$_3$Ir$_2$O$_7$ with $x=0.035$ and $x=0.071$. Once electrons are introduced into the bilayer spin-orbit assisted Mott insulator Sr$_3$Ir$_2$O$_7$, previous studies have identified the appearance of a low temperature structural distortion and have suggested the presence of a competing electronic instability in the phase diagram of this material. Our measurements resolve a lowering of the structural symmetry from monoclinic $C2/c$ to monoclinic $P2_1/c$ and the creation of two unique Ir sites within the chemical unit cell as the lattice distorts below a critical temperature $T_S$. Details regarding the modifications to oxygen octahedral rotations and tilting through the transition are discussed as well as the evolution of the low temperature distorted lattice as a function of carrier substitution.Comment: 8 pages, 4 figure

Multistage Zeeman deceleration of metastable neon

A supersonic beam of metastable neon atoms has been decelerated by exploiting the interaction between the magnetic moment of the atoms and time-dependent inhomogeneous magnetic fields in a multistage Zeeman decelerator. Using 91 deceleration solenoids, the atoms were decelerated from an initial velocity of 580m/s to final velocities as low as 105m/s, corresponding to a removal of more than 95% of their initial kinetic energy. The phase-space distribution of the cold, decelerated atoms was characterized by time-of-flight and imaging measurements, from which a temperature of 10mK was obtained in the moving frame of the decelerated sample. In combination with particle-trajectory simulations, these measurements allowed the phase-space acceptance of the decelerator to be quantified. The degree of isotope separation that can be achieved by multistage Zeeman deceleration was also studied by performing experiments with pulse sequences generated for $^{20}$Ne and $^{22}$Ne.Comment: 16 pages, 15 figure