Time-Reversal Symmetry Violation in Molecules Induced by Nuclear Magnetic Quadrupole Moments

Recent measurements in paramagnetic molecules improved the limit on the electron electric dipole moment (EDM) by an order of magnitude. Time-reversal ($T$) and parity ($P$) symmetry violation in molecules may also come from their nuclei. We point out that nuclear $T$, $P$-odd effects are amplified in paramagnetic molecules containing deformed nuclei, where the primary effects arise from the $T$, $P$-odd nuclear magnetic quadrupole moment (MQM). We perform calculations of $T$, $P$-odd effects in the molecules TaN, ThO, ${\mathrm{ThF}}^{+}$, ${\mathrm{HfF}}^{+}$, YbF, HgF, and BaF induced by MQMs. We compare our results with those for the diamagnetic TlF molecule, where the $T$, $P$-odd effects are produced by the nuclear Schiff moment. We argue that measurements in molecules with MQMs may provide improved limits on the strength of $T$, $P$-odd nuclear forces, on the proton, neutron, and quark EDMs, on quark chromo-EDMs, and on the QCD $\theta$ term and $CP$-violating quark interactions.