  In the pseudogap phase of the cuprate, a thermal Hall response of neutral
objects has been recently detected experimentally, which continuously persists
into the antiferromagnetic insulating phase. In this work, we study the
transport properties of neutral spinons as the elementary excitation of a doped
Mott insulator, which is governed by a mutual Chern-Simons topological gauge
structure. We show that such a chiral spinon as a composite of an $S=1/2$ spin
sitting at the core of a supercurrent vortex, can contribute to the thermal
Hall effect, thermopower, and Hall effect due to its intrinsic transverse
(cyclotron) motion under internal fictitious fluxes. In particular, the
magnitudes of the transport coefficients are phenomenologically determined by
two basic parameters: the doping concentration and $T_c$, quantitatively
consistent with the experimental measurements including the signs and
qualitative temperature and magnetic field dependence. Combined with the
predictions of the spinon longitudinal transport properties, including the
Nernst and spin Hall effects, a phenomenological description of the pseudogap
phase is established as characterized by the neutral spinon excitations, which
eventually become "confined" with an intrinsic superconducting transition at
$T_c$. Finally, within this theoretical framework, the "order to order" phase
transition between the superconducting and antiferromagnetic insulating phases
are briefly discussed, with the thermal Hall monotonically increasing into the
latter.
