Microscopic origin of the mobility enhancement at a spinel/perovskite oxide heterointerface revealed by photoemission spectroscopy

The spinel/perovskite heterointerface $\gamma$-Al$_2$O$_3$/SrTiO$_3$ hosts a two-dimensional electron system (2DES) with electron mobilities exceeding those in its all-perovskite counterpart LaAlO$_3$/SrTiO$_3$ by more than an order of magnitude despite the abundance of oxygen vacancies which act as electron donors as well as scattering sites. By means of resonant soft x-ray photoemission spectroscopy and \textit{ab initio} calculations we reveal the presence of a sharply localized type of oxygen vacancies at the very interface due to the local breaking of the perovskite symmetry. We explain the extraordinarily high mobilities by reduced scattering resulting from the preferential formation of interfacial oxygen vacancies and spatial separation of the resulting 2DES in deeper SrTiO$_3$ layers. Our findings comply with transport studies and pave the way towards defect engineering at interfaces of oxides with different crystal structures.Comment: Accepted as Rapid Communications in Physical Review

Photoemission Spectroscopy and the Unusually Robust One Dimensional Physics of Lithium Purple Bronze

Temperature dependent photoemission spectroscopy in Li0.9Mo6O17 contributes to evidence for one dimensional physics that is unusually robust. Three generic characteristics of the Luttinger liquid are observed, power law behavior of the k-integrated spectral function down to temperatures just above the superconducting transition, k-resolved lineshapes that show holon and spinon features, and quantum critical (QC) scaling in the lineshapes. Departures of the lineshapes and the scaling from expectations in the Tomonaga Luttinger model can be partially described by a phenomenological momentum broadening that is presented and discussed. The possibility that some form of 1d physics obtains even down to the superconducting transition temperature is assessed.Comment: submitted to JPCM, Special issue article "Physics in one dimension

Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr2IrO4 opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating

Elemental Topological Insulator with a Tunable Fermi Level: Strained \alpha-Sn on InSb(001)

We report on the epitaxial fabrication and electronic properties of a topological phase in strained \alpha-Sn on InSb. The topological surface state forms in the presence of an unusual band order not based on direct spin-orbit coupling, as shown in density functional and GW slab-layer calculations. Angle-resolved photoemission including spin detection probes experimentally how the topological spin-polarized state emerges from the second bulk valence band. Moreover, we demonstrate the precise control of the Fermi level by dopants.Comment: version 2 with supplementary informatio

Understanding Battery Interfaces by Combined Characterization and Simulation Approaches: Challenges and Perspectives

Driven by the continuous search for improving performances, understanding the phenomena at the electrode/electrolyte interfaces has become an overriding factor for the success of sustainable and efficient battery technologies for mobile and stationary applications. Toward this goal, rapid advances have been made regarding simulations/modeling techniques and characterization approaches, including high-throughput electrochemical measurements coupled with spectroscopies. Focusing on Li-ion batteries, current developments are analyzed in the field as well as future challenges in order to gain a full description of interfacial processes across multiple length/timescales; from charge transfer to migration/diffusion properties and interphases formation, up to and including their stability over the entire battery lifetime. For such complex and interrelated phenomena, developing a unified workflow intimately combining the ensemble of these techniques will be critical to unlocking their full investigative potential. For this paradigm shift in battery design to become reality, it necessitates the implementation of research standards and protocols, underlining the importance of a concerted approach across the community. With this in mind, major collaborative initiatives gathering complementary strengths and skills will be fundamental if societal and environmental imperatives in this domain are to be met

Optimalisasi Keuntungan Ayam Geprek Menggunakan Pemrograman Linear Metode Simpleks

KFC Geprek Abang Junior milik Ibu Syamsiah, merupakan salah satu Usaha Mikro Kecil dan Menengah (UMKM) yang sedang berkembang di Pontianak. Pada usaha ayam geprek, permasalahan harga dan keterbatasan bahan baku untuk memproduksi juga mempengaruhi penjualan yang dapat menyebabkan keuntungan menjadi tidak maksimal. Penelitian ini dilakukan dengan tujuan untuk merumuskan penyelesaian masalah dalam mengoptimalkan keuntungan pada Usaha Mikro Kecil Menengah (UMKM) dari bisnis KFC Geprek Abang Junior milik Ibu Syamsiah. Metode simpleks merupakan sebuah cara untuk menyelesaikan soal pemrograman linear di mana pengulangan prosedur matematis itu dilakukan untuk menguji titik-titik sudut sehingga ditemukan penyelesaian optimal. Data yang digunakan dalam penelitian ini merupakan data yang diperoleh dari hasil wawancara bisnis KFC Geprek Abang Junior milik Ibu Syamsiah. Berdasarkan penelitian melalui program linear metode simpleks, diperoleh hasil perhitungan optimalisasi diantaranya jumlah produksi ayam geprek sebanyak 300 porsi dan hati ayam crispy sebanyak 30 porsi per hari, sehingga didapatkan keuntungan maksimal sebesar Rp1.260.000,00