Observation of the dynamic Jahn-Teller effect in the excited states of nitrogen-vacancy centers in diamond

Abstract

The optical transition linewidth and emission polarization of single nitrogen-vacancy (NV) centers are measured from 5 K to room temperature. Inter-excited state population relaxation is shown to broaden the zero-phonon line and both the relaxation and linewidth are found to follow a T 5 dependence for T < 100 K. This dependence indicates that the dynamic Jahn-Teller effect is the dominant dephasing mechanism for the NV optical transitions at low temperatures.PACS numbers: 71.70. Ej, 81.05.ug The negatively-charged nitrogen-vacancy (NV) center in diamond has attracted much scientific interest due to its unique spin and optical properties. Long coherence lifetimes of the ground electron spin state at room temperature, up to milliseconds in recent reports [1], have enabled fundamental studies of coherent electronelectron [2] and electron-nuclear coupling [3,4,5] of a small number of spins in a solid. Spin-selective optical transitions enable readout of the electron spin at room temperature which is critical for both high sensitivity magnetometry [6] and quantum information processing. Moreover, at cryogenic temperatures, it is proposed that these spin-dependent optical transitions [7,8] could provide an interface between spins and photons as needed in schemes for scalable quantum computation [9, 10] and quantum communication [11,12]. The success of such schemes depends on the coherence properties of the emitted photons which in turn are determined by the coherence properties of the NV excited states.Dephasing of the excited state of an optical transition manifests itself in an energy broadening of the transition. For solid-state defects, the broadening can be observed in the zero-phonon line (ZPL), the optical transition in which no net phonon is emitted or absorbed. Typically the ZPL width exhibits a T 7 dependence on temperature T , and the dephasing mechanism is attributed to electron-phonon scattering mediated by a quadratic electron-phonon interaction [13,14]. In this work we first measured the polarization of the emitted ZPL photons as a function of T . The NV excited state consists of an orbital doublet and a change in the emitted polarization indicates population transfer between the two orbital states. We found that the emission polarization is strongly temperature dependent and that the population relaxation rate between the orbital states varies as T 5 . Next we measured the temperature dependence of the ZPL width. A T 5 dependence was again found, indicating that for T < 100 K the ZPL broadening is mainly determined by excited state population transfer. Most significantly, the T 5 dependence observed is evidence of the dynamic Jahn-Teller (DJT) effect in the NV excited states, as explained below.The NV center in diamond has trigonal symmetry (point group C3v) and consists of a single substitutional nitrogen with a nearest neighbor carbon vacancy. The NV axis (z axis) can point along any of the four 111 crystallographic axes. The ground state has 3 A 2 symmetry (spin-triplet/orbital-singlet) and is s...

Optical Polarization of Nuclear Spins in Silicon Carbide

“…In diamond, both the nitrogen-vacancy center's ES-spin coherence and its off-resonantly pumped ESLAC-derived DNP rapidly decline below T ¼ 50 K [34]. This diminishment is due to the deactivation of the dynamic Jahn-Teller effect, in which phonons motionally narrow pairs of ES electronic orbitals into a single coherent spin resonance [57][58][59]. In SiC, at T ¼ 5 K, the base temperature of our cryostat, we observe both a coherent ES spin resonance [ Figs.…”

Control of Spin Defects in Wide-Bandgap Semiconductors for Quantum Technologies

“…This diffusion occurs when charge instabilities around the NV À center reset during certain types of photoexcitation, particularly that of the 532-nm off-resonant laser [96], [97], causing slight shifts in the electrostatic environment which are sensed by the NV À center resulting in shifts of the optical transition energies. Over a series of measurements with repeated reinitializations by a 532-nm laser, this leads to a spectrally broadened peak [92]. However, with reionizations along the NV 0 zero-phonon line at 575 nm, the linewidth of the NV À center optical transitions becomes transform limited [49].…”

“…These transitions are spin dependent [85] and provide another means of spin-state readout [95]. It should be noted that in most samples, these peaks are broadened beyond the transform limited linewidth as a result of spectral diffusion [92]. This diffusion occurs when charge instabilities around the NV À center reset during certain types of photoexcitation, particularly that of the 532-nm off-resonant laser [96], [97], causing slight shifts in the electrostatic environment which are sensed by the NV À center resulting in shifts of the optical transition energies.…”

“…This detailed structure of the ES is only optically resolvable at cryogenic temperatures (T G 20 K) [90], above which Jahn-Teller distortions cause significant broadening of these levels [92]. The room temperature operation of the NV À center is enabled by an averaging process that leads to an orbital singlet-like ES with a spin triplet [93].…”

Density-Functional-Theory Calculations of Formation Energy of the Nitrogen-Doped Diamond

“…Defect introductions in diamond can make it adsorb light to produce colored material [1][2][3]. Like in other crystals, defects in diamond can be a vacancy, atomic interstitial, substitution, or impurity (dopant) defect with the very common dopant in diamond is nitrogen [4][5][6]. Recently, the study of defective diamond has attracted much attention because of its broad applications in technology such as for active materials of ultrafast electronic devices [7][8][9] and in jewelry industries [1][2][3].…”