2026/03/15 by Mahbub Rahaman, Analabha Roy, Anindita Roy
Materials Science · Physics and Astronomy · #Chain (unit) #Crystal (programming language) #Discrete time and continuous time #Floquet theory #Order (exchange) #Quantum many-body systems #Quasicrystal Structures and Properties #Spin (aerodynamics) #Topological Materials and Phenomena
paper · pdf · doi:10.1103/rzj3-fb2n
published in Physical review. B./Physical review. B 114(3) (American Physical Society)
openalex publication_date 2026/07/01 · openalex created_date 2026/07/02 · openalex updated_date 2026/08/05
We propose a novel protocol to realize discrete time-crystal (DTC) order in clean, periodically driven spin-1/2 chains. In each drive cycle, a global spin flip is followed by a two-tone flat-band segment. This flat-band segment engineers a fully degenerate Floquet quasienergy spectrum, suppresses thermalization, and stabilizes a robust period-doubled subharmonic response. Using exact time evolution, we identify a pronounced subharmonic peak at half the drive frequency in the Fourier spectrum of the order parameter, thereby providing clear evidence for the emergence of stable DTC. The resulting phase is insensitive to system size, interaction strength, and interaction range; however, it remains sensitive to spin-rotation errors (εr), which can destabilize the subharmonic response. Compared with disorder-induced many-body localized (MBL) and disorder-free dynamically many-body localized (DMBL) DTCs, we find that the exact flat-band protocol offers a broader tunability of drive parameters, whereas MBL and DMBL based DTCs are more resistant to εr. In particular, the εr sensitivity can be suppressed by incorporating additional spin-spin interactions that have modest deviations from the ideal flat-band protocol. This manifests itself in a robust DTC response over a finite window of spin-coupling strengths and drive frequencies. Our results establish flat-band driving as a versatile and experimentally relevant route to DTC order in disorder-free spin systems and motivate further exploration of nonequilibrium phases.