Related papers: Excitons and Optical Response in Excitonic Insulat…

Traditional routes to Charge-Density-Wave in transition metal dichalcogenides, relying on Fermi surface nesting or Jahn-Teller instabilities have recently been brought into question. While this calls for exploration of alternative views,…

1$T$-TaSe$_2$ is a prototypical charge density wave (CDW) material for which electron-phonon coupling and associated lattice distortion play an important role in driving and stabilizing the CDW phase. Here, we investigate the lattice…

The origin of charge density waves (CDW) in TiSe$_2$ has long been debated, mainly due to the difficulties in identifying the timescales of how and when the excitonic pairing and electron-phonon coupling (EPC) come into play. Without a…

The evolution of the charge carrier concentrations and mobilities are examined across the charge-density-wave (CDW) transition in TiSe2. Combined quantum oscillation and magnetotransport measurements show that a small electron pocket…

$(TaSe_4)_2I$ is a well-studied quasi-one-dimensional compound long-known to have a charge-density wave (CDW) transition around 263 K. We argue that the critical fluctuations of the pinned CDW order parameter near the transition can be…

The strong coupling between lattice modes and charges which leads to the formation of charge density waves in materials such as the transition-metal dichalcogenides may also give rise to superconductivity in the same materials, mediated by…

The nonlocal correlation mechanism between excitonic pairs is considered for a two dimensional exciton system. On the base of the unitary decomposition of the usual electron operator, we include the electron phase degrees of freedom into…

We investigated temperature ($T$) dependent ultrafast near-infrared (NIR) transient reflectivity dynamics in coexisting superconducting (SC) and charge density wave (CDW) phases of two-dimensional 2H-NbSe$_{2}$ using NIR and visible…

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…

An excitonic insulator (EI) is an unconventional quantum phase of matter in which excitons, bound pairs of electrons and holes, undergo Bose--Einstein condensation, forming a macroscopic coherent state. While its existence was first…

A charge-density-wave (CDW) is characterized by a dynamical order parameter consisting of a time-dependent amplitude and phase, which manifest as optically-active collective modes of the CDW phase. Studying the behaviour of such collective…

The spontaneous condensation of excitons in the excitonic insulating phase has been reported in Ta$_2$NiSe$_5$ below 325 K. In this context, we present the temperature-dependent optical pump optical probe spectroscopy of Ta$_2$NiSe$_5$,…

Axion electrodynamics in condensed matter could emerge from the formation of charge density waves (CDWs) in Weyl semimetals. (TaSe$_4$)$_2$I was proposed to be the first material platform for realizing axionic CDW that may host topological…

An incommensurate charge density wave (CDW) is a periodic modulation of charge that breaks translational symmetry incongruently with the underlying lattice. Its low-energy excitations, the phason, are collective, gapless phase fluctuations.…

We provide optical reflectivity data collected over a broad spectral range and as a function of temperature on the ErTe$_3$ and HoTe$_3$ materials, which undergo two consecutive charge-density-wave (CDW) phase transitions at $T_{CDW1}$= 265…

Charge density waves (CDWs) appear in numerous condensed matter platforms, ranging from high-Tc superconductors to quantum Hall systems. Despite such ubiquity, there has been a lack of direct experimental study on boundary states that can…

We study the dynamical phase transition out of an excitonic insulator phase after photo-excitation using a time-dependent extension of the selfconsistent GW method. We connect the evolution of the photoemission spectra to the dynamics of…

Recently, we employed electronic polarization-resolved Raman spectroscopy to reveal the strongly correlated excitonic insulator (EI) nature of Ta2NiSe5, Volkov et al. [arXiv:2007.07344], and also showed that for…

Ta$_2$NiSe$_5$ is an excitonic insulator candidate showing the semiconductor/semimetal-to-insulator (SI) transition below $T_{\text{c}}$ = 326 K. However, since a structural transition accompanies the SI transition, deciphering the role of…

We investigate the controversial case of charge-density-wave (CDW) order in single layer 1T-TiSe$_2$ by employing the density functional perturbation theory with on-site Hubbard interactions. The results emphasize the crucial role of…