The interface between the insulating oxides LaAlO3 and SrTiO3 exhibits a superconducting two-dimensional electron system that can be modulated by a gate voltage. While the conductivity has been probed extensively and gating of the superconducting critical temperature has been demonstrated, the question as to whether, and if so how, the gate tunes the superfluid density and superconducting order parameter needs to be answered. We present local magnetic susceptibility, related to the superfluid density, as a function of temperature, gate voltage, and location. We show that the temperature dependence of the superfluid density at different gate voltages collapses to a single curve that is characteristic of a full superconducting gap. Further, we show that the dipole moments observed in this system are not modulated by the gate voltage.

The geometrically frustrated double perovskite Ba${}_2$YMoO${}_6$ is characterized by quantum $s=1/2$ spins at the Mo${}^{5+}$ sites of an undistorted fcc lattice. Previous low-temperature characterization revealed an absence of static long-range magnetic order and suggested a nonmagnetic spin-singlet ground state. We report unique time-of-flight and triple-axis neutron spectroscopy of Ba${}_2$YMoO${}_6$ that shows a 28 meV spin excitation with a bandwidth of $\sim$4 meV, which vanishes above $\sim$125 K. We identify this as the singlet-triplet excitation that arises out of a singlet ground state, and further identify a weaker continuum of magnetic states within the gap, reminiscent of spin-polaron states arising due to weak disorder.

Low-temperature magnetic ac susceptibility measurements of single-crystal dipolar spin ice Dy2Ti2O7 are presented. The relaxation is found to exhibit thermally activated Arrhenius behavior with an activation energy of 9.79 K ($\sim${}9Jeff), which is not consistent with a simple scaling of 6Jeff, as previously found for Ho2Ti2O7. There are distinct quantifiable differences between Dy2Ti2O7 and Ho2Ti2O7 absorption spectra. The measured dynamics does not agree with simulations based on current magnetic monopole theory nor thermal relaxation measurements, but instead freezes out at a faster rate.