BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:Low dimensionality effects in single layers of transition metal di
 chalcogenides
DTSTART:20161216T151500
DTSTAMP:20260511T074641Z
UID:465f56ec6e8c5eb085fd8fe590c50cdd63c0f5a1a8004f772b81ab46
CATEGORIES:Conferences - Seminars
DESCRIPTION:M.M. Ugeda\,  Department of Physics\, University of Californ
 ia\, Berkeley CIC nanoGUNE\, 20018 Donostia-San Sebastian Ikerbasque\, B
 asque Foundation for Science\nTransition metal dichalcogenides (TMDs) are
  subject to effects of reduced dimensionality when thinned down from bulk
  to the single-layer limit\, which may impact their fundamental propertie
 s and overall response. In this talk I will illustrate the influence of s
 uch effects on the electronic and optoelectronic properties of MBE-grown 2
 D TMD semiconductors and metals. I will first discuss the direct experim
 ental observation of extraordinarily high exciton binding energy and band
  structure renormalization in a single layer of semiconducting TMD [1] d
 ue to reduced screening by using a combination of STS and photoluminescen
 ce spectroscopy. We have also studied the role of interlayer coupling and
  layer dependent carrier screening on the electronic structure of few lay
 er MoSe2 [2]. We find that the electronic quasiparticle bandgap decrease
 s by nearly 1 eV when going from one layer to three. Finally\, I will de
 scribe the fate of the collective electronic phases\, i.e. charge density
  wave order and superconductivity\, of NbSe2 in the single layer limit [
 3]. We demonstrate that - in striking contrast to recent theoretical pr
 edictions - 3 x 3 CDW order remains intact in 2D.  Superconductivity als
 o still remains but its critical temperature is depressed to 1.9 K. Our S
 TS measurements at 5 K reveal a CDW gap of Δ = 4 meV at the Fermi energ
 y\, which is accessible via STS due to the removal of bands crossing the 
 Fermi level in the 2D limit. These findings enable to experimentally rul
 e out two well-known mechanisms proposed to explain the origin of the CDW
  in NbSe2\, and our results impose stringent constraints on any future t
 heory of CDW formation in NbSe2.\n \nReferences:\n[1] M. M. Ugeda\, et
  al.\, Nature Materials 13\, 1091 (2014). \n[2] A. J. Bradley\, M. M. 
 Ugeda\, et al.\, Nano Letters 15\, 2594 (2015).\n[3] M. M. Ugeda\, et
  al.\, Nature Physics 12\, 92 (2016).\n 
LOCATION:CE 1 5 https://plan.epfl.ch/?room==CE%201%205
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR