  Metal-based electronics is attractive for fast and radiation-hard electronic
circuits and remains one of the longstanding goals for researchers. The
emergence of 1T-TaS$_2$, a layered material exhibiting strong charge density
wave (CDW) driven resistivity switching that can be controlled by an external
stimulus such as electric field and optical pulses, has triggered a renewed
interest in metal-electronics. Here we demonstrate a negative differential
resistor (NDR) using electrically driven CDW phase transition in an
asymmetrically designed T-junction made up of 1T-TaS$_2$/2H-MoS$_2$ van der
Waals heterostructure. The principle of operation of the proposed device is
governed by majority carrier transport and is distinct from usual NDR devices
employing tunneling of carriers, thus avoids the bottleneck of weak tunneling
efficiency in van der Waals heterojunctions. Consequently, we achieve a peak
current density in excess of $10^5$ nA$\mu$m$^{-2}$, which is about two orders
of magnitude higher than that obtained in typical layered material based NDR
implementations. The peak current density can be effectively tuned by an
external gate voltage as well as photo-gating. The device is robust against
ambiance-induced degradation and the characteristics repeat in multiple
measurements over a period of more than a month. The findings are attractive
for the implementation of active metal-based functional circuits.
