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A topological insulator protected by time-reversal symmetry is realized via spin-orbit interaction-driven band inversion. The topological phase in the Bi(1-x)Sb(x) system is due to an odd number of band inversions. A related spin-orbit system, the Pb(1-x)Sn(x)Te, has long been known to contain an even number of inversions based on band theory. Here we(More)
In topological crystalline insulators (TCIs), topology and crystal symmetry intertwine to create surface states with distinct characteristics. The breaking of crystal symmetry in TCIs is predicted to impart mass to the massless Dirac fermions. Here, we report high-resolution scanning tunneling microscopy studies of a TCI, Pb(1-x)Sn(x)Se that reveal the(More)
The tunability of topological surface states and controllable opening of the Dirac gap are of fundamental and practical interest in the field of topological materials. In the newly discovered topological crystalline insulators (TCIs), theory predicts that the Dirac node is protected by a crystalline symmetry and that the surface state electrons can acquire(More)
According to classical theory of phase transition, fluctuations in systems with low dimensions are so violent that the phase boundary between unstable and metastable states would be smeared. In this experiment, we measure the growth of surface fluctuations on an unstable polymer film with a thickness , h 0 = 5.1 nm, which is much less than the spinodal(More)
The high-temperature superconducting cuprate La(2-x)Sr(x)CuO(4) (LSCO) shows several phases ranging from antiferromagnetic insulator to metal with increasing hole doping. To understand how the nature of the hole state evolves with doping, we have carried out high-resolution Compton scattering measurements at room temperature together with first-principles(More)
We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel Li_{x}Mn_{2}O_{4}, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process(More)
Metallic liquid silicon at 1787 K is investigated using x-ray Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Our results show persistence of covalent bonding in liquid silicon and provide support for the occurrence of theoretically predicted liquid-liquid(More)
LiFePO4 is a battery cathode material with high safety standards due to its unique electronic structure. We performed systematic experimental and theoretical studies based on soft X-ray emission, absorption, and hard X-ray Raman spectroscopy of LixFePO4 nanoparticles and single crystals. The results clearly show a non-rigid electron-state reconfiguration of(More)
Bismuth chalcogenides and lead telluride/selenide alloys exhibit exceptional thermoelectric properties that could be harnessed for power generation and device applications. Since phonons play a significant role in achieving these desired properties, quantifying the interaction between phonons and electrons, which is encoded in the Eliashberg function of a(More)
Bonding characteristics of liquid boron at 2500 K are studied by using high-resolution Compton scattering. An excellent agreement is found between the measurements and the corresponding Car-Parrinello molecular dynamics simulations. Covalent bond pairs are clearly shown to dominate in liquid boron along with the coexistence of diffuse pairs. Our study(More)