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As the field of exfoliated van der Waals electronics grows to include complex heterostructures, the variety of available in-plane symmetries and geometries becomes increasingly valuable. In this work, we present an efficient chemical vapor transport synthesis of NbSe2I2 with the triclinic space group P1̅. This material contains Nb–Nb dimers and an in-plane crystallographic angle γ = 61.3°. We show that NbSe2I2 can be exfoliated down to few-layer and monolayer structures and use Raman spectroscopy to test the preservation of the crystal structure of exfoliated thin films. The crystal structure was verified by single-crystal and powder X-ray diffraction methods. Density functional theory calculations show triclinic NbSe2I2 to be a semiconductor with a band gap of around 1 eV, with similar band structure features for bulk and monolayer crystals. The physical properties of NbSe2I2 have been characterized by transport, thermal, optical, and magnetic measurements, demonstrating triclinic NbSe2I2 to be a diamagnetic semiconductor that does not exhibit any phase transformation below room temperature.
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Elemental excitations in MoI3 one-dimensional van der Waals nanowires
We report the polarization-dependent Raman spectra of exfoliated MoI3, a van der Waals material with a “true one-dimensional” crystal structure that can be exfoliated to individual atomic chains. The temperature evolution of several Raman features reveals an anomalous behavior suggesting a phase transition of magnetic origin. Theoretical considerations indicate that MoI3 is an easy-plane antiferromagnet with alternating spins along the dimerized chains and with inter-chain helical spin ordering. The calculated frequencies of phonons and magnons are consistent with the interpretation of the experimental Raman data. The obtained results shed light on the specifics of the phononic and magnonic states in MoI3 and provide a strong motivation for further study of this unique material with potential for future spintronic applications.
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- Award ID(s):
- 1922312
- PAR ID:
- 10439942
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 121
- Issue:
- 22
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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