  Uncooled Terahertz (THz) photodetectors (PDs) showing fast (ps) response and
high sensitivity (noise equivalent power (NEP) < $nWHz^{-1/2}$) over a broad
(0.5THz-10THz) frequency range are needed for applications in high-resolution
spectroscopy (relative accuracy ~ $10^{-11}$), metrology, quantum information,
security, imaging, optical communications. However, present THz receivers
cannot provide the required balance between sensitivity, speed, operation
temperature and frequency range. Here, we demonstrate an uncooled THz PD
combining the low (~2000 $k_{B}{\mu}m^{-2}$) electronic specific heat of high
mobility (> 50000 $cm^{2}V^{-1}s^{-1}$) hBN-encapsulated graphene with the
asymmetric field-enhancement produced by a bow-tie antenna resonating at 3 THz.
This produces a strong photo-thermoelectric conversion, which simultaneously
leads to a combination of high sensitivity (NEP $\leq$ 160 $pWHz^{-1/2}$), fast
response time ($\leq 3.3 ns$) and a four orders of magnitude dynamic range,
making our devices the fastest, broadband, low noise, room temperature THz PD
to date.
