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Riley JM, Meevasana W, Bawden L, et al. Negative electronic compressibility and tunable spin splitting in WSe2. Nat Nanotechnol. 2015;10(12):1043-7doi: 10.1038/nnano.2015.217.
Riley, J. M., Meevasana, W., Bawden, L., Asakawa, M., Takayama, T., Eknapakul, T., Kim, T. K., Hoesch, M., Mo, S. K., Takagi, H., Sasagawa, T., Bahramy, M. S., & King, P. D. (2015). Negative electronic compressibility and tunable spin splitting in WSe2. Nature nanotechnology, 10(12), 1043-7. https://doi.org/10.1038/nnano.2015.217
Riley, J M, et al. "Negative electronic compressibility and tunable spin splitting in WSe2." Nature nanotechnology vol. 10,12 (2015): 1043-7. doi: https://doi.org/10.1038/nnano.2015.217
Riley JM, Meevasana W, Bawden L, Asakawa M, Takayama T, Eknapakul T, Kim TK, Hoesch M, Mo SK, Takagi H, Sasagawa T, Bahramy MS, King PD. Negative electronic compressibility and tunable spin splitting in WSe2. Nat Nanotechnol. 2015 Dec;10(12):1043-7. doi: 10.1038/nnano.2015.217. Epub 2015 Sep 21. PMID: 26389661.
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Nat Nanotechnol. 2015 Dec;10(12):1043-7. doi: 10.1038/nnano.2015.217. Epub 2015 Sep 21.

Negative electronic compressibility and tunable spin splitting in WSe2.

Nature nanotechnology

J M Riley, W Meevasana, L Bawden, M Asakawa, T Takayama, T Eknapakul, T K Kim, M Hoesch, S-K Mo, H Takagi, T Sasagawa, M S Bahramy, P D C King

Affiliations

  1. SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK.
  2. Diamond Light Source, Harwell Campus, Didcot OX11 0DE, UK.
  3. School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
  4. NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
  5. Materials and Structures Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan.
  6. Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
  7. Max Planck Institute for Solid State Research, Stuttgart 70569, Germany.
  8. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley California 94720, USA.
  9. Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
  10. RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.

PMID: 26389661 DOI: 10.1038/nnano.2015.217

Abstract

Tunable bandgaps, extraordinarily large exciton-binding energies, strong light-matter coupling and a locking of the electron spin with layer and valley pseudospins have established transition-metal dichalcogenides (TMDs) as a unique class of two-dimensional (2D) semiconductors with wide-ranging practical applications. Using angle-resolved photoemission (ARPES), we show here that doping electrons at the surface of the prototypical strong spin-orbit TMD WSe2, akin to applying a gate voltage in a transistor-type device, induces a counterintuitive lowering of the surface chemical potential concomitant with the formation of a multivalley 2D electron gas (2DEG). These measurements provide a direct spectroscopic signature of negative electronic compressibility (NEC), a result of electron-electron interactions, which we find persists to carrier densities approximately three orders of magnitude higher than in typical semiconductor 2DEGs that exhibit this effect. An accompanying tunable spin splitting of the valence bands further reveals a complex interplay between single-particle band-structure evolution and many-body interactions in electrostatically doped TMDs. Understanding and exploiting this will open up new opportunities for advanced electronic and quantum-logic devices.

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