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Applied magnetic fields are an important tuning parameter for artificial spin ice (ASI) systems, as they can drive phase transitions between different magnetic ground states, or tune through regimes with high populations of emergent magnetic excitations (e.g., monopole-like quasiparticles). Here, using simulations supported by experiments, we investigate the thermodynamic properties and magnetic phases of square and quadrupolar ASI as a function of applied in-plane magnetic fields. Monte Carlo simulations are used to generate field-dependent maps of the magnetization, the magnetic specific heat, the thermodynamic magnetization fluctuations, and the magnetic order parameters, all under equilibrium conditions. These maps reveal the diversity of magnetic orderings and the phase transitions that occur in different regions of the phase diagrams of these ASIs, and are experimentally supported by magneto-optical measurements of the equilibrium "magnetization noise" in thermally-active ASIs., 12 pages, 7 figures, in press at Physical Review B

Zeeman effect induced by the magnetic field introduces a splitting between the two valleys at K

At cryogenic temperatures, the photoluminescence (PL) spectrum of monolayer WSe

We present a study of photoluminescence dynamics of CdTe/ZnTe quantum dots using subpicosecond excitation correlation technique. The quantum dot is excited by pairs of light pulses with tuned delay between them. The variation of relative intensity of photoluminescence lines corresponding to different charge states is observed in a timescale of 20 ps when changing delay between pulses. We explain the observed effect by a simple model that assumes different trapping dynamics of electrons and holes in the quantum dot.