Browsing by Author "Hall, Joshua"

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  • Reversible crystalline-to-amorphous phase transformation in monolayer MoS2 under grazing ion irradiation
    (2020-04) Valerius, Philipp; Kretschmer, Silvan; Senkovskiy, Boris V.; Wu, Shilong; Hall, Joshua; Herman, Alexander; Ehlen, Niels; Ghorbani-Asl, Mahdi; Grueneis, Alexander; Krasheninnikov, Arkady V.; Michely, Thomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    By combining scanning tunneling microscopy, low-energy electron diffraction, photoluminescence and Raman spectroscopy experiments with molecular dynamics simulations, a comprehensive picture of the structural and electronic response of a monolayer of MoS 2 to 500 eV Xe + irradiation is obtained. The MoS 2 layer is epitaxially grown on graphene/Ir(1 1 1) and analyzed before and after irradiation in situ under ultra-high vacuum conditions. Through optimized irradiation conditions using low-energy ions with grazing trajectories, amorphization of the monolayer is induced already at low ion fluences of 1.5 × 10 14 ions cm -2 and without inducing damage underneath the MoS 2 layer. The crystalline-to-amorphous transformation is accompanied by changes in the electronic properties from semiconductor-to-metal and an extinction of photoluminescence. Upon thermal annealing, the re-crystallization occurs with restoration of the semiconducting properties, but residual defects prevent the recovery of photoluminescence.
  • Tomonaga-Luttinger Liquid in a Box: Electrons Confined within MoS2 Mirror-Twin Boundaries
    (2019-03-28) Jolie, Wouter; Murray, Clifford; Weiss, Philipp S.; Hall, Joshua; Portner, Fabian; Atodiresei, Nicolae; Krasheninnikov, Arkady; Busse, Carsten; Komsa, Hannu-Pekka; Rosch, Achim; Michely, Thomas
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Two- or three-dimensional metals are usually well described by weakly interacting, fermionic quasiparticles. This concept breaks down in one dimension due to strong Coulomb interactions. There, low-energy electronic excitations are expected to be bosonic collective modes, which fractionalize into independent spin- and charge-density waves. Experimental research on one-dimensional metals is still hampered by their difficult realization, their limited accessibility to measurements, and by competing or obscuring effects such as Peierls distortions or zero bias anomalies. Here we overcome these difficulties by constructing a well-isolated, one-dimensional metal of finite length present in MoS2 mirror-twin boundaries. Using scanning tunneling spectroscopy we measure the single-particle density of the interacting electron system as a function of energy and position in the 1D box. Comparison to theoretical modeling provides unambiguous evidence that we are observing spin-charge separation in real space.