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Electron-hole pair excitations in semiconductors have been predicted to be able to give rise to a highly correlated many-body ground state, the excitonic insulator (EI). Under appropriate conditions below a critical temperature (Tc),…

Strongly Correlated Electrons · Physics 2023-01-18 Aidan Delgado , Carolin Dusold , Jingwei Jiang , Adam Cronin , Steven G. Louie , Felix R. Fischer

The interplay between topology and correlations can generate a variety of quantum phases, many of which remain to be explored. Recent advances have identified monolayer WTe2 as a promising material for doing so in a highly tunable fashion.…

Motivated by recent experiments, which give strong evidence for an excitonic insulating phase in $\rm TmSe_{0.45}Te_{0.55}$, we developed a scheme to quantitatively construct, for generic two-band models, the phase diagram of an excitonic…

Strongly Correlated Electrons · Physics 2009-11-11 B. Hülsen , F. X. Bronold , H. Fehske , K. Yonemitsu

We show that the coupling to vibrational degrees of freedom can drive a semimetal excitonic-insulator quantum phase transition in an one-dimensional two-band f-c electron system at zero temperature. The insulating state typifies an…

Strongly Correlated Electrons · Physics 2015-06-17 N. V. Phan , K. W. Becker , H. Fehske

Coulomb attraction between electrons and holes in a narrow-gap semiconductor or a semimetal is predicted to lead to an elusive phase of matter dubbed 'excitonic insulator'. However, direct observation of such electronic instability remains…

Strongly Correlated Electrons · Physics 2021-08-09 Kwangrae Kim , Hoon Kim , Jonghwan Kim , Changil Kwon , Jun Sung Kim , B. J. Kim

Half a century ago, Mott noted that tuning the carrier density of a semimetal towards zero produces an insulating state in which electrons and holes form bound pairs. It was later argued that such pairing persists even if a semiconducting…

Materials Science · Physics 2017-05-23 Z. Zhu , R. D. McDonald , A. Shekhter , B. J. Ramshaw , K. A. Modic , F. F. Balakirev , N. Harrison

A panoply of unconventional electronic states has been observed in moir\'e superlattices. Engineering similar bosonic phases remains, however, largely unexplored. We report the observation of a bosonic correlated insulator in WSe2/WS2…

Using the projector-based renormalization method we investigate the formation of the excitonic insulator phase in the two-dimensional (2D) spinless Falicov-Kimball model with dispersive $f$ electrons and address the existence of excitonic…

Strongly Correlated Electrons · Physics 2015-05-27 Van-Nham Phan , Holger Fehske , Klaus W. Becker

The fundamental idea of the excitonic insulator (EI) driven by electron-hole correlations in narrow-gap semiconductors or semimetals was originally proposed in the 1960s, and only theoretical studies had been advanced for a long time.…

Strongly Correlated Electrons · Physics 2024-12-25 Tatsuya Kaneko , Yukinori Ohta

Realizing an excitonic insulator phase from narrow-gap semiconductors remains challenging, as unambiguous experimental signatures are difficult to establish. Ta$_2$NiSe$_5$ has been widely regarded as a leading candidate, yet the nature of…

Materials Science · Physics 2025-12-11 Keyu Wei , Yixuan Luo , Kenji Watanabe , Takashi Taniguchi , Yanfeng Guo , Xiaoxiang Xi

We consider an extended spinless Falicov--Kimball model at an arbitrary doping level, focusing on the range of parameter values where a uniform excitonic insulator is stabilised at half-filling. We compare the properties of possible uniform…

Strongly Correlated Electrons · Physics 2025-12-30 D. I. Golosov

Exciton-polaritons are quasiparticles consisting of a linear superposition of photonic and excitonic states, offering potential for nonlinear optical devices. The excitonic component of the polariton provides a finite Coulomb scattering…

Mesoscale and Nanoscale Physics · Physics 2017-03-20 Lucas C. Flatten , David M. Coles , Zhengyu He , David. G. Lidzey , Robert A. Taylor , Jamie H. Warner , Jason M. Smith

Excitonic insulators host a condensate of electron-hole pairs at equilibrium, giving rise to collective many-body effects. Although several materials have emerged as excitonic insulator candidates, evidence of long-range coherence is…

Excitonic insulators are long-sought-after quantum materials predicted to spontaneously open a gap by the Bose condensation of bound electron-hole pairs, namely, excitons, in their ground state. Since the theoretical conjecture, extensive…

In the 1960s, it was proposed that in small indirect band-gap materials, excitons can spontaneously form because the density of carriers is too low to screen the attractive Coulomb interaction between electrons and holes. The result is a…

Materials Science · Physics 2024-05-31 Zhi Li , Muhammad Nadeem , Zengji Yue , David Cortie , Michael Fuhrer , Xiaolin Wang

Experiments on quantum materials have uncovered many interesting quantum phases ranging from superconductivity to a variety of topological quantum matter including the recently observed fractional quantum anomalous Hall insulators. The…

Strongly Correlated Electrons · Physics 2024-11-15 Sanfeng Wu , Leslie M. Schoop , Inti Sodemann , Roderich Moessner , Robert J. Cava , N. P. Ong

The exciton insulator (EI) is a unique many-body ground state of condensed, spontaneously formed excitons (electron-hole pairs) in equilibrium, distinct from conventional band or Mott insulators. Originally proposed over half a century ago,…

Strongly Correlated Electrons · Physics 2026-03-26 Yande Que , Clara Rebanal , Liam Watson , Michael Fuhrer , Michał Papaj , Bent Weber , Iolanda Di Bernardo

The excitonic insulator (EI) is an exotic ground state of narrow-gap semiconductors and semimetals arising from spontaneous condensation of electron-hole pairs bound by attractive Coulomb interaction. Despite research on EIs dating back to…

Electron-hole bound pairs, or excitons, are common excitations in semiconductors. They can spontaneously form and ``condense'' into a new insulating ground state -- the so-called excitonic insulator -- when the energy of electron-hole…

Recently, detailed calculations of the excitonic insulator phase model adapted to the case of 1\textit{T}-TiSe$_2$ have been presented. Through the spectral function theoretical photoemission intensity maps can be generated which are in…

Strongly Correlated Electrons · Physics 2015-05-13 C. Monney , H. Cercellier , F. Clerc , C. Battaglia , E. F. Schwier , C. Didiot , M. G. Garnier , H. Beck , P. Aebi