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Charge-density wave and superconducting dome in TiSe2 from electron-phonon interaction
Matteo Calandra1, Francesco Mauri
1IMPMC, Université Paris 6, CNRS, 4 Place Jussieu, 75015 Paris, France.
Physical Review Letters
|June 15, 2011
Summary
Titanium diselenide (TiSe2) exhibits a charge-density wave instability at low temperatures. First-principles calculations reveal that pressure suppresses this instability, stabilizing superconductivity through electron-phonon interactions, not excitonic mechanisms.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Physics
Background:
- Titanium diselenide (TiSe2) is known to exhibit a charge-density wave (CDW) instability at low temperatures.
- Superconductivity in TiSe2 can be induced by external pressure or chemical doping, such as copper intercalation.
- Understanding the interplay between CDW order and superconductivity is crucial for materials design.
Purpose of the Study:
- To investigate the pressure-induced phase diagram of TiSe2 using first-principles calculations.
- To elucidate the mechanisms responsible for the suppression of the charge-density wave instability under pressure.
- To determine the role of electron-phonon interactions in the pressure-dependent superconducting behavior of TiSe2.
Main Methods:
- Density Functional Theory (DFT) based first-principles calculations.
- Analysis of electronic band structure and Fermi surface nesting.
- Calculation of phonon dispersion and electron-phonon coupling constants.
- Thermodynamic modeling of phase transitions.
Main Results:
- First-principles calculations accurately reproduce the experimentally observed charge-density wave ordering below 4 GPa.
- The disappearance of the CDW at higher pressures is attributed to the stiffening of short-range force constants, rather than changes in Fermi surface nesting.
- The superconducting transition temperature (Tc) as a function of pressure is fully explained by the electron-phonon interaction, without invoking excitonic effects.
- The study confirms that competing orders and superconducting domes can arise within the electron-phonon interaction framework.
Conclusions:
- First-principles calculations provide a robust description of the pressure-temperature phase diagram of TiSe2.
- The transition from CDW order to a superconducting state is governed by changes in lattice dynamics and electron-phonon coupling.
- The findings support the universal applicability of electron-phonon interaction theories for understanding complex phase behaviors in materials like TiSe2.
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