Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R43: Discrete Time Crystal Signatures in Driven Spin SystemsInvited Session
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Sponsoring Units: DCMP Room: BCEC 210B |
Thursday, March 7, 2019 8:00AM - 8:36AM |
R43.00001: DTC signatures in NV Centers: Initial Discovery and Late-breaking Results Invited Speaker: Mikhail Lukin TBD |
Thursday, March 7, 2019 8:36AM - 9:12AM |
R43.00002: Can Prethermal Regimes explain the lastest observations of DTC signatures in driven spin systems? Invited Speaker: Chetan Nayak TBD |
Thursday, March 7, 2019 9:12AM - 9:48AM |
R43.00003: Observation of Discrete-Time-Crystal Signatures in an Ordered Dipolar Many-Body System Invited Speaker: Sean Barrett The rich dynamics and phase structure of driven systems include the recently described phenomenon of the discrete time crystal (DTC), a robust phase which spontaneously breaks the discrete time translation symmetry of its driving Hamiltonian. Experiments in trapped ions and diamond nitrogen vacancy centers have recently shown evidence for this DTC order. Here, we report nuclear magnetic resonance (NMR) observations of DTC signatures in a third, strikingly different, system: an ordered spatial crystal. This system is expected to be even farther from the regime of many-body localization (MBL) than those studied in the earlier experiments. We study the 100% occupied crystal lattice of spin-1/2 31P nuclei in ammonium dihydrogen phosphate (ADP), with chemical formula NH4H2PO4. ADP also contains spin-1/2 1H nuclei (99.98% abundant) and spin-1 14N nuclei (99.64% abundant). Implementing the DTC pulse sequence on the 31P spins, we observe robust oscillations at half the drive frequency (“DTC oscillations” for brevity) across orders of magnitude in interaction time. We also study the decay mechanism of the DTC oscillations, with two results. First, we show by generating a time-reversed DTC echo that the density matrix is more coherent than the original DTC sequence reveals. Second, we show that the effect of interactions during the nonzero pulse duration of the DTC sequence limits our ability to observe the intrinsic lifetime of the DTC oscillations [1,2]. In this work, we exploited both the long coherence times of our sample, and our ability to use NMR pulse sequences to edit the spin Hamiltonian. This suggests that NMR can be a useful probe of the physics of out-of-equilibrium, driven many-body systems. |
Thursday, March 7, 2019 9:48AM - 10:24AM |
R43.00004: What NMR detection of DTC signatures may be telling us. Invited Speaker: Vedika Khemani TBD |
Thursday, March 7, 2019 10:24AM - 11:00AM |
R43.00005: Temporal Order in Periodically Driven Spins in small NMR spin Clusters Invited Speaker: Sreejith Ganesh Jaya We present the results of experimental studies on the magnetization response of star-shaped clusters of initially unentangled N=4, 10, and 37 nuclear spin-1/2 moments when subjected to inexact pi-pulse sequences. We find that an Ising coupling between the center and the satellite spins results in robust period-2 magnetization oscillations. On the other hand, control experiments (using alternate Isotopes ) without the Ising coupling do not show a robust time period. The period is stable against bath effects, but the amplitude decays with a timescale that depends on the inexactness of the pulse. Numerical simulations of the system reveal a simple semiclassical picture in which the rigidity of the period is due to a randomizing effect from the Larmor precession due to the magnetization of the surrounding spins. The timescale with stable periodicity increases with the net initial magnetization, even in the presence of perturbations and absence of disorder, indicating a robust temporal ordered phase for large systems with finite magnetization per spin. We also present results of numerical simulations of the system with simple model couplings to a bath. |
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