We introduce and investigate material junctions as a generic and tunable electronic platform for the realization of exotic non-Hermitian (NH) topological states of matter, where the NH character is induced by the surface self-energy of a thermal reservoir. As a conceptually rich and immediately experimentally realizable example, we consider a three-dimensional topological insulator (TI) coupled to a ferromagnetic lead. Remarkably, the symmetry-protected TI is promoted in a dissipative fashion to a non-symmetry-protected NH Weyl phase with no direct Hermitian counterpart and which exhibits robustness against any perturbation. The transition between a gapped phase and the NH Weyl phase may be readily tuned experimentally with the magnetization direction of the ferromagnetic lead. Given the robustness of this exotic nodal phase, our general analysis also applies to, e.g., a two-dimensional electron gas close to criticality in proximity to a ferromagnetic lead. There, the predicted bulk Fermi arcs are directly amenable to surface spectroscopy methods such as angle-resolved photoemission spectroscopy.

Using discrete element simulations, we demonstrate that critical behavior for yielding in soft disk and sphere packings is independent of the distance to isostaticity over a wide range of dimensionless pressures. Jammed states are explored via quasistatic shear at fixed pressure, and the statistics of the dimensionless shear stress $\mu$ of these states obey a scaling description with a diverging length scale $\xi \propto |\mu -{\mu }_c{|}^{-\nu }$. The critical scaling functions and values of the scaling exponents are nearly independent of distance to isostaticity despite the large range of pressures studied. Our results demonstrate that yielding of jammed systems represents a distinct nonequilibrium critical transition from the isostatic critical transition which has been demonstrated by previous studies. Our results may also be useful in deriving nonlocal rheological descriptions of granular materials, foams, emulsions, and other soft particulate materials.

Based on first-principles calculations and a symmetry-based indicator analysis, we find a class of topological crystalline insulators (TCIs) with a $C_2$ rotation anomaly in a family of Zintl compounds, including ${\mathrm{Ba}}_3{\mathrm{Cd}}_2{\mathrm{As}}_4$, ${\mathrm{Ba}}_3{\mathrm{Zn}}_2{\mathrm{As}}_4$, and ${\mathrm{Ba}}_3{\mathrm{Cd}}_2{\mathrm{Sb}}_4$. The nontrivial band topology protected by the coexistence of $C_2$ rotation symmetry and time-reversal symmetry $T$ leads to two surface Dirac cones at generic momenta on both top and bottom surfaces perpendicular to the rotation axis. In addition, $(d-2)$-dimensional helical hinge states are also protected along the hinge formed by two side surfaces parallel to the rotation axis. We develop a method based on the nested Wilson loop technique to prove the existence of these surface Dirac cones due to a $C_2$ anomaly and precisely locate them as demonstrated in studying these TCIs. The helical hinge states are also calculated. Finally, we show that external strain can be used to tune the topological phase transitions among TCIs, strong $Z_2$ topological insulators, and trivial insulators.