Supermassive Black Holes (SMBHs) are ubiquitous in the contemporary universe.

But when and where did they form? Recent discovery of quasars hosting SMBHs

more massive than a billion solar masses at redshifts z > 7, when the universe

was less than 700 Megayear old, provides a substantial challenge to current

paradigm of a hierarchical structure formation, which tells us that massive objects

form late in the history. In my talk, I will discuss the latest progress (in) and our

contribution to understanding of formation of these most enigmatic objects.

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Oxide materials are the most abundant compound in the earth’s crust and possess a wide range of electrical, optical, and magnetic properties. For instance, insulators, high quality metals, dielectrics, ferroelectrics, piezoelectrics, semiconductors, ferromagnetics, transparent conductors, superconductors, and nonlinear optic materials have all been produced using oxide materials. Oxide materials have enormous potential, particularly as the fundamental building block of a new generation of electronic devices. We create these materials by artificially layering various atoms including oxygen at the single atomic level and discovering novel properties that are likely to find applications in electronic, magnetic, optical and electromechanical devices. I will discuss how our research [1-6] played a role in understanding the fundamental solid state phenomena at the atomic scale and the discovery of new materials so that we can use them to develop new oxide nanoelectronic devices. Atomic layer control of novel oxide heterointerfaces may provide some of the answers that we need to continue the electronics revolution, particularly for nanoscale devices with new functionality that are currently being developed and can be applied to various fields.

1. “Polar Metals by Geometric Design”, Nature 533, 68 (2016)

2. “Emergence of Room-temperature Ferroelectricity at Reduced Dimensions” Science, 349, 1314 (2015)

3. “Giant piezoelectricity on Si for hyper-active MEMS” Science, 334, 958 (2011)

4. “Metallic and insulating oxide interfaces controlled by electronic correlations” Science, 331, 886 (2011)

5. “Creation of a two-dimensional electron gas at an oxide interface grown on silicon” Nature Communications, 1, 94 (2010)

6. “Ferroelastic switching for nanoscale nonvolatile magnetoelectric devices” Nature Materials, 9, 309 (2010)

The OMC1 BN/KL outflow, located immediately behind the Orion Nebula, may have been triggered

by the dynamic decay of a non-hierarchical system of massive stars that resulted in the formation of a

compact, AU-scale binary, or more likely, a protostellar merger (Bally et al. 2011, 2015). The event

ejected the ∼ 20 M binary or merger remnant (suspected to be radio source I), the ∼12 Solar-mass

BN object, and infrared source n, and released more than 1048 ergs of energy about 500 years ago.

I will present ALMA observations of CO and the continuum with 1" angular resolution and multi-

conjugate adaptive optics images at 0.06" resolution in the 2.12 μm H2 and 1.64 μm [FeII] emission

lines. Explosive outflows similar to Orion may be associated with the ejection of runaway stars, the

production of IR-flares with luminosities between novae and supernovae, and have profound feedback

impact on their parent molecular clouds. Massive protostars accreting at high rates develop AU-scale

photospheres that resemble red supergiants. Protostellar mergers may be relatively common in massive

star forming regions because of the large cross-sections of bloated massive protostars, the high stellar

volume density of forming clusters, and the dissipative nature of dense cloud cores and clumps.

References:

Bally, J., Ginsburg, A., Silvia, D., et al. 2015, A&A, 579, 130

Bally, J., Cunningham, N. J., Moeckel, N., et al. 2011, ApJ, 727, 113

 

Astrometric observations tell us that the matter content of the Universe is dominated by dark matter, a quantity that finds no explanation within the Standard Model of particle interactions. Moreover, popular theories that would explain dark matter in terms of new, high-energy physics have as yet no empirical support from studies at high energy colliders. It is possible, rather, that essential clues as to its nature may first come from the appearance of light, weakly coupled new physics, to which low-energy, precision tests of the Standard Model are exquisitely sensitive. In this context, I will discuss an experimental anomaly in $^8$Be nuclear transitions that may be interpreted as evidence for a new, weak force of some 12 fm in range. I will review the experimental evidence, its interpretation and implications, and emphasize what further experimental tests can be done to probe the experimental anomaly and its interpretation.

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Due to coexisting electron-correlation and the spin-orbit interaction, 5d transition-metal oxides, e.g., complex iridates, have received a great deal of attention. However, our understanding of the system advances rather slowly owing to limited experimental approaches. In this colloquium, I will discuss our recent research on layered (2D) iridate thin-films of A₂IrO₄ (A = Ba, Sr, Ca). Note that the Ba₂IrO₄ and Ca₂IrO₄ phases do not exist in nature, yet their thermodynamically meta-stable phases can be synthesized using an epitaxy-stabilizing technique. Moreover, I will show artificial heterostructures of one-dimensional (1D) iridates consisting of linear Ir-O-Ir stripes. This approach of investigating artificial 1D systems opens a new avenue to explore low-dimensional quantum physics. Based on our recent experimental investigations of transport, optical spectroscopy, and resonant inelastic x-ray scattering, I will discuss our current understanding of the complex iridates and their topological properties due to coexisting strong electron-correlation and spin-orbit interaction.

Direct neutrino mass measurements probe Beyond Standard Model physics ex-

tensions which are employed to explain the finite neutrino masses, which are

in contradiction to the minimal Standard Model of Particle Physics but now

firmly established through the observation of neutrino flavor oscillations. While

being insensitive to the absolute neutrino mass scale oscillation experiments

provide lower limits, depending on the neutrino mass hierarchy. The upcom-

ing KATRIN experiment will improve the upper limits set by the Mainz and

Troitsk experiments (≤2 eV/c2 ) down to 200 meV/c2 and will probe the quasi

degenerate regime of neutrino mass hierarchy. I will discuss fundamentally new

laboratory approaches currently under development to either confirm a posi-

tive KATRIN result independently or to push the sensitivity limit towards the

40 meV/c2 range, the predicted lowest neutrino mass in case an inverted mass

hierarchy is realized in Nature. Major financial support by the U.S. Depart-

ment of Energy, Office of Science, Office of Nuclear Physics to the University of

Washington under Award Number DE-FG02-97ER41020 is acknowledged.

 

Conventional wisdom holds that quantum effects are washed out when the temperature becomes comparable to the quantized spacing between energy levels, and that the presence of a finite density of excitations above the ground state is antithetical to the stability of quantum coherent phenomena. However, the advent of modern techniques to cool and trap large collections of atoms, molecules and ions has stimulated a revival of interest in the behavior of isolated, interacting quantum systems. Recently it has been recognized that there exist "many-body localized" phases of matter that exhibit quantum dynamics even at infinite temperature, signalling a breakdown of conventional equilibrium statistical mechanics. I will discuss the intriguing and unusual properties of these inherently out-of-equilibrium systems, and outline their implications for our understanding of the phase structure of quantum many-particle systems.

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The electronic states of materials have an intrinsic angular momentum known as “spin”. The coupling between diffusive currents of spin and heat in materials is the basis of the emerging field of “spin caloritronics”. Analogous to a thermocouple where a temperature difference produces a voltage that can be used to measure temperature, heat currents in magnetic materials produce currents of spin that can be used to manipulate magnetization. Our work in this field takes advantage of recent advances in the measurement and understanding of heat transport at the nanoscale using ultrafast lasers. We use picosecond duration laser pulses as a source of heat (the pump) and detect changes in temperature and magnetization using a combination of thermoreflectance and magneto-optic Kerr effect (the probe). Our pump-probe optical methods enable us to generate enormous heat fluxes on the order of 100 GW m^-2 that persist for ~30 ps.

Spin caloritronics effects can be divided into two broad categories: effects arising from thermal excitations of independent electrons (spin-dependent Seebeck effect) and effects arising from collective excitations of spin waves (spin Seebeck effect). The spin-dependent Seebeck effect of a perpendicular ferromagnetic layer converts a heat current into a spin current, which in turn can be used to exert a thermal spin transfer torque on a second ferromagnetic layer with in-plane magnetization. Using a [Co,Ni] multilayer as the source of spin, an energy fluence of ≈4 J m^-2 creates thermal STT sufficient to induce ≈1% tilting of the magnetization of a 2 nm-thick CoFeB layer. We study the spin Seebeck effect driven by an interfacial temperature difference between electrons in a normal metal (Au or Cu) and spin-waves in a ferromagnetic insulator (Y₃Fe₅O₁₂). The spin Seebeck coefficient provides new insights on the coupling of excitations across material interfaces.

The need to store energy at high concentration in a way that is safe, efficient, and economical appears in several technologies: load balancing of the grid,  alternative energy schemes, and transportation beyond the standard model.   I will survey the proposed schemes, noting where the laws of physics put boundaries on what can be achieved.