  Terahertz (THz) communication is a promising technology for future wireless
networks due to its ultra-wide bandwidth. However, THz signals suffer from
severe attenuation and poor diffraction capability, making it vulnerable to
blocking obstacles. To compensate for these two shortcomings and improve the
system performance, an intelligent reflecting surface (IRS) can be exploited to
change the propagation direction and enhance the signal strength. In this
article, we investigate this promising ultra wide band (UWB) THz IRS
communication paradigm. We start by motivating our research and describing
several potential application scenarios. Then, we identify major challenges
faced by UWB THz IRS communications. To overcome these challenges, several
effective key techniques are developed, i.e., the time delayer-based sparse
radio frequency antenna structure, delay hybrid precoding and IRS deployment.
Simulation results are also presented to compare the system performance for
these proposed techniques, thus demonstrating their effectiveness. Finally, we
highlight several open issues and research opportunities for UWB THz IRS
communications.
