Identification and tunable optical coherent control of transition-metal spins in silicon carbide

Abstract

Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration in communication technology is hindered by the fact that their optical transitions lie outside telecom wavelength bands. Several transition-metal impurities in silicon carbide do emit at and near telecom wavelengths, but knowledge about their spin and optical properties is incomplete.We present all-optical identification and coherent control of molybdenum-impurity spins in silicon carbide with transitions at near-infrared wavelengths. Our results identify spin S = 1/2 for both the electronic ground and excited state, with highly anisotropic spin properties that we apply for implementing optical control of ground-state spin coherence. Our results show optical lifetimes of ∼60 ns and inhomogeneous spin dephasing times of ∼0.3 µs, establishing relevance for quantum spin-photon interfacing.2 Electronic spins of lattice defects in wide-bandgap semiconductors have come forward as an important platform for quantum technologies 1 , in particular for applications that require both manipulation of long-coherent spin and spin-photon interfacing via bright optical transitions. In recent years this field showed strong development, with demonstrations of distribution and storage of non-local entanglement in networks for quantum communication 2-6 , and quantum-enhanced field-sensing 7-11 . The nitrogen-vacancy defect in diamond is the material system that is most widely used 12,13 and best characterized 14-16 for these applications.However, its zero-phonon-line (ZPL) transition wavelength (637 nm) is not optimal for integration in standard telecom technology, which uses near-infrared wavelength bands where losses in optical fibers are minimal. A workaround could be to convert photon energies between the emitter-resonance and telecom values 17-19 , but optimizing these processes is very challenging.This situation has been driving a search for similar lattice defects that do combine favorable spin properties with bright emission directly at telecom wavelength. It was shown that both diamond and silicon carbide (SiC) can host many other spin-active color centers that could have suitable properties 20-23 (where SiC is also an attractive material for its established position in the semiconductor device industry 24,25 ). However, for many of these color centers detailed knowledge about the spin and optical properties is lacking. In SiC the divacancy 26-28 and silicon vacancy 10,29-31 were recently explored, and these indeed show millisecond homogeneous spin coherence times with bright ZPL transitions closer to the telecom band.We present here a study of transition-metal impurity defects in SiC, which exist in great variety [32][33][34][35][36][37] . There is at least one case (the vanadium impurity) that has ZPL transitions at telecom wavel...

Vanadium spin qubits as telecom quantum emitters in silicon carbide

“…Transition metal ions such as chromium in ruby have long been used in laser systems for their 3d shell optical transitions, often with emission in the near-infrared (NIR) (12,13). Recent studies using chromium, molybdenum, and vanadium in silicon carbide (SiC) have shown that they may be equally relevant for quantum applications, combining both brightness and (near-)telecom emission in a technologically mature material (14)(15)(16). Among these ions, vanadium V 4+ is the only fully telecom transition metal emitter, covering the entire O-band spectrum (1278 to 1388 nm), depending on its substitutional silicon site in the 4H and 6H polytypes of SiC (17)(18)(19).…”

Electrical charge state identification and control for the silicon vacancy in 4H-SiC

“…More recently, point defects in silicon carbide (4H-SiC) have gained attention as a more devicefriendly alternative, offering a platform to merge existing semiconductor processing capabilities with the quantum technology of the future. 9,10 Recent testaments to the viability of 4H-SiC as a quantum host include single-photon emission from, and coherent control of, the silicon vacancy (V Si ), [11][12][13] carbon antisitevacancy pair (C Si V C ), 14 transition metal 15 and silicon-carbon divacancy (V Si V C ) 16 spins at room temperature, as well as observations of millisecond spin coherence times for V Si 17 and V Si V C 18 at cryogenic temperatures. Hitherto, the desired quantum properties of defects in 4H-SiC have been established for specific charge states only, with the remainder being dark and exhibiting no identified spin signals.…”

Silicon carbide color centers for quantum applications

“…Among these the V Si [40] V C V Si , [41,42] the N C V Si [43,44] in various polytypes. In addition, some transition metal color centers such as Ti [45], V [45][46][47], and Mo [48]. On the right in red, color centers in SiC observed as single-photon sources with the maximum brightness observed in cts s −1 , among this the CAV [49,50], Si C [22], oxidation [22] and annealing [51] related and unknown, 3C IR emitters [52].…”

“…It has ZPL at 1033 nm, spin number 1, and ZFS 3.3 GHz. In [48] a Mo impurity with ZPL transitions at 1076 nm (in p-type 4H-SiC) and 1121 nm (in p-type 6H-SiC) were studied. These impurities were associated with the Mo 5+ (4d1) charge state with S=1/2 for both the electronic ground and excited state.…”

“…Data for V Si are from [54, 56, 58, 60, 62, 69-73, 76-79, 147]; DV from [53, 55, 81-85]; IR unknown emitters from [52]; CAV form [49, 87-90, 92]; D1 color centre from [22] and related references. ; oxydation related defects from[93]; annealing related from[51]; N C V Si from[43,44,[94][95][96]; Ti from[100]; Cr from[45,101,102]; V from[45][46][47]103]; Mo from[45,48].…”