Oscar Tjernberg

Topological crystalline insulator states in Pb1−xSnxSe

Topological insulators are a class of quantum materials in which time-reversal symmetry, relativistic effects and an inverted band structure result in the occurrence of electronic metallic states on the surfaces of insulating bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical results have suggested the existence of topological crystalline insulators (TCIs), a class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in ensuring topological protection. In this study we show that the narrow-gap semiconductor Pb(1-x)Sn(x)Se is a TCI for x  =  0.23. Temperature-dependent angle-resolved photoelectron spectroscopy demonstrates that the material undergoes a temperature-driven topological phase transition from a trivial insulator to a TCI. These experimental findings add a new class to the family of topological insulators, and we anticipate that they will lead to a considerable body of further research as well as detailed studies of topological phase transitions.

Oxygen structures on Fe(110)

The adsorption of oxygen on a Fe(110) single crystal has been studied by means of high resolution photoelectron spectroscopy (HRPES) and scanning tunneling microscopy (STM). Core level spectra were ...

Coherent d-Wave Superconducting Gap in Underdoped La2-xSrxCuO4 by Angle-Resolved Photoemission Spectroscopy

We present angle-resolved photoemission spectroscopy (ARPES) data on moderately underdoped La

Spin-polarized (001) surface states of the topological crystalline insulator Pb0.73Sn0.27Se

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Electronic structure near the 1/8-anomaly in La-based cuprates

Sr

An experimental setup for high resolution 10.5 eV laser-based angle-resolved photoelectron spectroscopy using a time-of-flight electron analyzer

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Magnetism of exposed and Co-capped Fe nanoparticles

CuO

Observation of topological crystalline insulator surface states on (111)-oriented Pb1-xSnxSe films

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A spin- and angle-resolving photoelectron spectrometer

at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple {\it d}-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La

When low-and high-energy electronic responses meet in cuprate superconductors

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