Recent timing observation reported that the radio pulsar PSR J1734 - 3333 with a rotating period P = 1.17 ~ { } s is slowing down with a period derivative \dot { P } = 2.28 \times 10 ^ { -12 } s s ^ { -1 } .
Its derived braking index n = 0.9 \pm 0.2 is the lowest value among young radio pulsars with the measured braking indices .
In this Letter , we attempt to investigate the influence of the braking torque caused by the interaction between the fall-back disk and the strong magnetic field of the pulsar on the spin evolution of PSR J1734 - 3333 .
Analytical result show that this braking torque is obviously far more than that by magnetic dipole radiation for pulsars with spin period of > 0.1 s , and play an important role during the spin-down of the pulsars .
Our simulated results indicate that , for some typical neutron star parameters , the braking index and the period derivative approximately in agreement with the measured value of PSR J1734 - 3333 if the material inflow rate in the fallback disk is 2 \times 10 ^ { 17 } g s ^ { -1 } .
In addition , our scenario can account for the measured braking indices of four young pulsars .
However , our predicted X-ray luminosity are 1 -2 order of magnitude higher than the observation .
We proposed that this discrepancy may originate from the instability of fall-back disk .