We examine the discontinuous first-order superfluid He3 A to B transition in the vicinity of the polycritical point (2.232 mK and 21.22 bar). We find path-dependent transitions: cooling at fixed pressure yields a well-defined transition line in the temperature-pressure plane, but this line can be reliably crossed by depressurizing at nearly constant temperature after transiting Tc at a higher pressure. This path dependence is not consistent with any of the standard B-phase nucleation mechanisms in the literature.

We present measurements of spin-orbit torques generated by Ir as a function of film thickness in sputtered Ir/CoFeB and Ir/Co samples. We find that Ir provides a dampinglike component of spin-orbit torque with a maximum spin-torque conductivity σDLeff=(1.4±0.1)×105-2eω-1m-1 and a maximum spin-torque efficiency of ζDL=0.042±0.005, which is sufficient to drive switching in a 0.8 nm film of CoFeB with perpendicular magnetic anisotropy. We also observe a surprisingly large fieldlike spin-orbit torque (FLT).

Two-dimensional (2D) hybrid organic-inorganic perovskites consisting of alternating organic and inorganic layers are a new class of layered structures. They have attracted increasing interest for photovoltaic, optoelectronic, and thermoelectric applications, where knowing their thermal transport properties is critical. We carry out both experimental and computational studies on thermal transport properties of 2D butylammonium lead iodide crystals and find their thermal conductivity is ultralow (below 0.3 W m-1 K-1) with very weak anisotropy (around 1.5) among layered crystals.

Moiré superlattices created by the twisted stacking of two-dimensional crystals can host electronic bands with flat energy dispersion in which enhanced interactions promote correlated electron states. The twisted double bilayer graphene (TDBG), where two Bernal bilayer graphene are stacked with a twist angle, is such a moiré system with tunable flat bands.

We study the transport properties for a family of geometrically frustrated models on the triangular lattice with an interaction scale far exceeding the single-particle bandwidth. Starting from the interaction-only limit, which can be solved exactly, we analyze the transport and thermodynamic behavior as a function of filling and temperature at the leading nontrivial order in the single-particle hopping. Over a broad range of intermediate temperatures, we find evidence of a DC resistivity scaling linearly with temperature and with typical values far exceeding the quantum of resistance h/e2.

The anomalous charge transport observed in some strongly correlated metals raises questions as to the universal applicability of Landau Fermi-liquid theory. The coherence temperature TFL for normal metals is usually taken to be the temperature below which T2 is observed in the resistivity. Below this temperature, a Fermi liquid with well-defined quasiparticles is expected. However, metallic ruthenates in the Ruddlesden-Popper family frequently show non-Drude low-energy optical conductivity and unusual ω/T scaling, despite the frequent observation of T2 dc resistivity.

Moiré superlattices of two-dimensional van der Waals materials have emerged as a powerful platform for designing electronic band structures and discovering emergent physical phenomena. A key concept involves the creation of long-wavelength periodic potential and moiré bands in a crystal through interlayer electronic hybridization or atomic corrugation when two materials are overlaid. Here we demonstrate a new approach based on spatially periodic dielectric screening to create moiré bands in a monolayer semiconductor.

We present a ring-type Mamyshev oscillator with only one amplification stage. The design allows self-starting via modulation of the pump power, high pulse performance, and is suitable for all-fiber integration. © 2021 OSA.

Serial synchrotron crystallography (SSX) is enabling the efficient use of small crystals for structure-function studies of biomolecules and for drug discovery. An integrated SSX system has been developed comprising ultralow background-scatter sample holders suitable for room and cryogenic temperature crystallographic data collection, a sample-loading station and a humid 'gloveless' glovebox. The sample holders incorporate thin-film supports with a variety of designs optimized for different crystal-loading challenges.

Single spin arrays can serve as a scalable qubit platform. Here, we report the observation of arrays of single spins which are optically accessible through strain-induced localized positive trions residing in WSe2/CrI3 heterostructures. © 2021 OSA.