Zero-gap semiconductor to excitonic insulator transition in Ta₂NiSe₅.

ABSTRACT: The excitonic insulator is a long conjectured correlated electron phase of narrow-gap semiconductors and semimetals, driven by weakly screened electron-hole interactions. Having been proposed more than 50 years ago, conclusive experimental evidence for its existence remains elusive. Ta₂NiSe₅ is a narrow-gap semiconductor with a small one-electron bandgap E_G of <50 meV. Below T_C=326 K, a putative excitonic insulator is stabilized. Here we report an optical excitation gap E_op ∼0.16 eV below T_C comparable to the estimated exciton binding energy E_B. Specific heat measurements show the entropy associated with the transition being consistent with a primarily electronic origin. To further explore this physics, we map the

SUBMITTER: Lu YF 

PROVIDER: S-EPMC5316885 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature