TiSe2

TiSe2
Name	Titanium diselenide
Formula	TiSe2

TiSe2 TiSe2 is a transition metal dichalcogenide associated with layered materials such as Graphene, MoS2, WS2, NbSe2, and TaS2. It has been studied in contexts connected to Condensed matter physics, Materials science, Solid state physics, Low-dimensional systems, and Quantum materials. Research on TiSe2 intersects work by groups at institutions such as MIT, Stanford University, Max Planck Society, University of Cambridge, and ETH Zurich.

Overview

TiSe2 is a layered compound containing titanium and selenium, related to families studied alongside Graphite, Black phosphorus, Boron nitride, Transition metal dichalcogenide materials, and members of the Van der Waals heterostructure community. It is notable for cooperative phenomena investigated in the context of Charge density wave, Superconductivity, Excitonic insulator proposals, Electron–phonon coupling, and interplay studied using techniques from Angle-resolved photoemission spectroscopy, Scanning tunneling microscopy, Raman spectroscopy, and X-ray diffraction. Prominent experimental and theoretical treatments have been produced by groups affiliated with Harvard University, University of California, Berkeley, Bell Labs, Los Alamos National Laboratory, and RIKEN.

Crystal structure and synthesis

TiSe2 crystallizes in a layered structure akin to the 1T polytype observed in compounds like 1T-TaS2 and 1T-TiTe2; the stacking resembles motifs cataloged in the Crystallography Open Database and studied with methods from X-ray crystallography, Neutron scattering, Electron microscopy, and Transmission electron microscopy. Synthetic routes include chemical vapor transport using agents referenced in procedures at Brookhaven National Laboratory and Argonne National Laboratory, flux growth employed by groups at Oak Ridge National Laboratory, and molecular beam epitaxy as developed at IBM Research and National Institute for Materials Science. Substrates used for exfoliation and epitaxy include SiO2, Sapphire, Graphene/SiC, and Mica; characterization often references standards from International Union of Crystallography and techniques standardized at National Institute of Standards and Technology.

Electronic properties and band structure

Band structure calculations and measurements place TiSe2 in dialogue with work on Density functional theory, GW approximation, and Dynamical mean field theory. Early angle-resolved photoemission spectroscopy studies at facilities like Diamond Light Source, Advanced Light Source, and SOLEIL compared TiSe2 to materials such as Bi2Se3 and Cuprates. Debates over semimetal versus small-gap semiconductor descriptions connect to theoretical frameworks developed by researchers at Princeton University, University of Tokyo, Columbia University, and ETH Zurich. Spin-orbit coupling effects and orbital character analyses reference methodologies from Perdew–Burke–Ernzerhof functionals and codes like VASP, Quantum ESPRESSO, and WIEN2k.

Charge density wave and phase transitions

The commensurate charge density wave (CDW) of TiSe2 at low temperature has been compared with CDW phenomena in LaTe3, 1T-TaSe2, and K0.3MoO3 and analyzed with conceptual tools used in studies of the Peierls transition, Fermi surface nesting, and Excitonic insulator scenarios. Experimental probes include Inelastic X-ray scattering, Neutron scattering, Ultrafast pump–probe spectroscopy, and Fourier transform scanning tunneling spectroscopy at facilities such as SLAC National Accelerator Laboratory and European XFEL. The temperature-dependent transition around ~200 K has been mapped in phase diagrams alongside pressure-driven transitions measured in high-pressure cells developed at Max Planck Institute for Solid State Research and CERN collaborations that examine emergence or suppression of CDW order and competing phases.

Optical and transport properties

Optical conductivity, reflectivity, and dielectric function measurements on TiSe2 use instrumentation common to groups at Imperial College London, University of Oxford, EPFL, and University of Illinois Urbana-Champaign. Data have been interpreted with models from Kubo formula implementations in computational packages from Lawrence Berkeley National Laboratory collaborations. Transport experiments measuring resistivity, Hall effect, and magnetoresistance compare TiSe2 to materials studied at Los Alamos National Laboratory and NIST, and examine signatures related to CDW gaps, carrier compensation, and mobility examined also in WTe2 and Cd3As2 studies. Ultrafast optical experiments link to transient phenomena reported by groups at MIT Lincoln Laboratory and FOM Institute AMOLF.

Intercalation, doping, and superconductivity

Intercalation and doping studies borrow techniques and concepts from research on Li-ion battery materials, intercalated graphite compounds studied at Bell Labs, and alkali-doped layered materials published by teams at Columbia University and Tohoku University. Alkali metal intercalation, copper-doping, and pressure-induced modifications have produced superconductivity in TiSe2-related systems, analogous to superconducting domes explored in Cu_xTiSe2 experiments and compared with superconductivity in Cuprates and Iron pnictides. Experimental discoveries of superconducting phases have been reported by collaborations including University of Geneva and University of Florida and investigated with muon spin rotation at Paul Scherrer Institute and tunneling spectroscopy at Johns Hopkins University.

Category:Transition metal dichalcogenides