| Summary: | Periodically driven (Floquet) systems are described by time-dependent Hamiltonians that possess discrete time translation symmetry. The spontaneous breaking of this symmetry leads to the emergence of a novel non-equilibrium phase of matter—the Discrete Time Crystal (DTC). In this paper, we propose a scheme to extend the lifetime of a DTC in a paradigmatic model—a translation-invariant Ising spin chain with nearest-neighbor interaction <i>J</i>, subjected to a periodic kick by a transverse magnetic field with frequency <inline-formula><math display="inline"><semantics><mfrac><mrow><mn>2</mn><mi>π</mi></mrow><mi>T</mi></mfrac></semantics></math></inline-formula>. This system exhibits the hallmark signature of a DTC—persistent sub-harmonic oscillations with frequency <inline-formula><math display="inline"><semantics><mfrac><mi>π</mi><mi>T</mi></mfrac></semantics></math></inline-formula>—for a wide parameter regime. Employing both analytical arguments as well as exact diagonalization calculations, we demonstrate that the lifetime of the DTC is maximized, when the interaction strength is tuned to an optimal value, <inline-formula><math display="inline"><semantics><mrow><mi>J</mi><mi>T</mi><mo>=</mo><mi>π</mi></mrow></semantics></math></inline-formula>. Our proposal essentially relies on an interaction-induced quantum interference mechanism that suppresses the creation of excitations, and thereby enhances the DTC lifetime. Intriguingly, we find that the period doubling oscillations can last eternally in even size systems. This anomalously long lifetime can be attributed to a time reflection symmetry that emerges at <inline-formula><math display="inline"><semantics><mrow><mi>J</mi><mi>T</mi><mo>=</mo><mi>π</mi></mrow></semantics></math></inline-formula>. Our work provides a promising avenue for realizing a robust DTC in various quantum emulator platforms.
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