1
|
Valley phonons and exciton complexes in a monolayer semiconductor. Nat Commun 2020; 11:618. [PMID: 32001715 PMCID: PMC6992782 DOI: 10.1038/s41467-020-14472-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 01/06/2020] [Indexed: 11/08/2022] Open
Abstract
The coupling between spin, charge, and lattice degrees of freedom plays an important role in a wide range of fundamental phenomena. Monolayer semiconducting transitional metal dichalcogenides have emerged as an outstanding platform for studying these coupling effects. Here, we report the observation of multiple valley phonons - phonons with momentum vectors pointing to the corners of the hexagonal Brillouin zone - and the resulting exciton complexes in the monolayer semiconductor WSe2. We find that these valley phonons lead to efficient intervalley scattering of quasi particles in both exciton formation and relaxation. This leads to a series of photoluminescence peaks as valley phonon replicas of dark trions. Using identified valley phonons, we also uncover an intervalley exciton near charge neutrality. Our work not only identifies a number of previously unknown 2D excitonic species, but also shows that monolayer WSe2 is a prime candidate for studying interactions between spin, pseudospin, and zone-edge phonons.
Collapse
|
2
|
Fiedler H, Gupta P, Kennedy J, Markwitz A. 28Si + ion beams from Penning ion source based implanter systems for near-surface isotopic purification of silicon. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:123305. [PMID: 30599550 DOI: 10.1063/1.5048949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 11/30/2018] [Indexed: 06/09/2023]
Abstract
Modern computing technology is based on silicon. To date, a cost-effective and easy to implement method to obtain isotopically pure silicon is highly desirable for attaining efficient heat dissipation in microelectronic devices and for hosting spin qubits in quantum computing. We propose that it is possible to use a 28Si+ ion beam to obtain an isotopically pure near-surface region in wafer silicon. However, this requires a highly stable, high current, and isotopically pure 28Si ion beam. This work presents and discusses the instrumentation details and experimental parameters involved in generating this required ion beam. Silane is used as the precursor gas and is decomposed in a Penning ion source to generate a 28Si+ ion beam. The influence of key ion source parameters such as the gas flow rate, magnetic field strength, and anode voltage is presented. An isotopically pure 28Si+ ion beam with 10 ± 0.5 μA current on the target is obtained at the GNS Science 40 kV ion implanter. The beam was observed to be stable for at least 8 h and contains less than 700 ppm of other Si isotopes. This high current and high purity provides opportunities to explore efficient modification of the isotopic distribution in a native Si substrate at ambient temperature. The results highlight opportunities offered by using Penning ion source based low energy ion implanters for the synthesis of isotopically modified Si surface regions-a technique also applicable to other materials such as diamonds and diamond-like carbon.
Collapse
Affiliation(s)
- Holger Fiedler
- National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - Prasanth Gupta
- National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | - John Kennedy
- National Isotope Centre, GNS Science, Lower Hutt, New Zealand
| | | |
Collapse
|
3
|
Morse KJ, Abraham RJS, DeAbreu A, Bowness C, Richards TS, Riemann H, Abrosimov NV, Becker P, Pohl HJ, Thewalt MLW, Simmons S. A photonic platform for donor spin qubits in silicon. SCIENCE ADVANCES 2017; 3:e1700930. [PMID: 28782032 PMCID: PMC5529058 DOI: 10.1126/sciadv.1700930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/19/2017] [Indexed: 05/25/2023]
Abstract
Donor spins in silicon are highly competitive qubits for upcoming quantum technologies, offering complementary metal-oxide semiconductor compatibility, coherence (T2) times of minutes to hours, and simultaneous initialization, manipulation, and readout fidelities near ~99.9%. This allows for many quantum error correction protocols, which will be essential for scale-up. However, a proven method of reliably coupling spatially separated donor qubits has yet to be identified. We present a scalable silicon-based platform using the unique optical properties of "deep" chalcogen donors. For the prototypical 77Se+ donor, we measure lower bounds on the transition dipole moment and excited-state lifetime, enabling access to the strong coupling limit of cavity quantum electrodynamics using known silicon photonic resonator technology and integrated silicon photonics. We also report relatively strong photon emission from this same transition. These results unlock clear pathways for silicon-based quantum computing, spin-to-photon conversion, photonic memories, integrated single-photon sources, and all-optical switches.
Collapse
Affiliation(s)
- Kevin J. Morse
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Rohan J. S. Abraham
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Adam DeAbreu
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Camille Bowness
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Timothy S. Richards
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Helge Riemann
- Leibniz-Institut für Kristallzüchtung, 12489 Berlin, Germany
| | | | - Peter Becker
- Physikalisch-Technische Bundesanstalt (PTB) Braunschweig, 38116 Braunschweig, Germany
| | | | - Michael L. W. Thewalt
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Stephanie Simmons
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| |
Collapse
|
4
|
Sekiguchi T, Steger M, Saeedi K, Thewalt MLW, Riemann H, Abrosimov NV, Nötzel N. Hyperfine structure and nuclear hyperpolarization observed in the bound exciton luminescence of Bi donors in natural Si. PHYSICAL REVIEW LETTERS 2010; 104:137402. [PMID: 20481913 DOI: 10.1103/physrevlett.104.137402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Indexed: 05/29/2023]
Abstract
As the deepest group-V donor in Si, Bi has by far the largest hyperfine interaction and also a large I = 9/2 nuclear spin. At zero field this splits the donor ground state into states having total spin 5 and 4, which are fully resolved in the photoluminescence spectrum of Bi donor bound excitons. Under a magnetic field, the 60 expected allowed transitions cannot be individually resolved, but the effects of the nuclear spin distribution, -9/2 < or = I(z) < or = 9/2, are clearly observed. A strong hyperpolarization of the nuclear spin towards I(z) = -9/2 is observed to result from the nonresonant optical excitation. This is very similar to the recently reported optical hyperpolarization of P donors observed by EPR at higher magnetic fields. We introduce a new model to explain this effect, and predict that it may be very fast.
Collapse
Affiliation(s)
- T Sekiguchi
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | | | | | |
Collapse
|
5
|
Yang A, Steger M, Sekiguchi T, Thewalt MLW, Ladd TD, Itoh KM, Riemann H, Abrosimov NV, Becker P, Pohl HJ. Simultaneous subsecond hyperpolarization of the nuclear and electron spins of phosphorus in silicon by optical pumping of exciton transitions. PHYSICAL REVIEW LETTERS 2009; 102:257401. [PMID: 19659118 DOI: 10.1103/physrevlett.102.257401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Indexed: 05/28/2023]
Abstract
We demonstrate a method which can hyperpolarize both the electron and nuclear spins of 31P donors in Si at low field, where both would be essentially unpolarized in equilibrium. It is based on the selective ionization of donors in a specific hyperfine state by optically pumping donor bound exciton hyperfine transitions, which can be spectrally resolved in 28Si. Electron and nuclear polarizations of 90% and 76%, respectively, are obtained in less than a second, providing an initialization mechanism for qubits based on these spins, and enabling further ESR and NMR studies on dilute 31P in 28Si.
Collapse
Affiliation(s)
- A Yang
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Steger M, Yang A, Stavrias N, Thewalt MLW, Riemann H, Abrosimov NV, Churbanov MF, Gusev AV, Bulanov AD, Kovalev ID, Kaliteevskii AK, Godisov ON, Becker P, Pohl HJ. Reduction of the linewidths of deep luminescence centers in 28Si reveals fingerprints of the isotope constituents. PHYSICAL REVIEW LETTERS 2008; 100:177402. [PMID: 18518336 DOI: 10.1103/physrevlett.100.177402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Indexed: 05/26/2023]
Abstract
Dramatic reductions of the linewidths of well-known deep centers in 28Si reveal "isotopic fingerprints" of the constituents. The approximately 1014 meV Cu center, thought to be either a Cu pair or an isolated Cu, is shown to contain four Cu atoms, and the approximately 780 meV Ag center is shown to contain four Ag. The approximately 944 meV ;{*}Cu center, thought to be a different configuration of a Cu pair, in fact contains three Cu and one Ag, and a new two-Cu two-Ag center is found. The approximately 735 meV center, previously assigned to Fe, actually contains Au and three Cu. This suggests a family of four-atom (Cu, Ag, Au) centers.
Collapse
Affiliation(s)
- M Steger
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Yang A, Steger M, Karaiskaj D, Thewalt MLW, Cardona M, Itoh KM, Riemann H, Abrosimov NV, Churbanov MF, Gusev AV, Bulanov AD, Kaliteevskii AK, Godisov ON, Becker P, Pohl HJ, Ager JW, Haller EE. Optical detection and ionization of donors in specific electronic and nuclear spin States. PHYSICAL REVIEW LETTERS 2006; 97:227401. [PMID: 17155840 DOI: 10.1103/physrevlett.97.227401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Indexed: 05/12/2023]
Abstract
We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.
Collapse
Affiliation(s)
- A Yang
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, V5A 1S6 Canada
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Cardona M, Meyer TA, Thewalt MLW. Temperature dependence of the energy gap of semiconductors in the low-temperature limit. PHYSICAL REVIEW LETTERS 2004; 92:196403. [PMID: 15169425 DOI: 10.1103/physrevlett.92.196403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Indexed: 05/24/2023]
Abstract
The temperature dependence of the electronic states and energy gaps of semiconductors is an old but still important experimental and theoretical topic. Remarkably, extant results do not clarify the asymptotic T-->0 behavior. Recent breakthroughs in the spectroscopy of enriched 28Si allow us to measure changes in the band gap over the liquid 4He temperature range with an astounding precision of one part in 10(8), revealing a T4.0+/-0.2 decrease with increasing T. This is in excellent agreement with a theoretical argument predicting an exponent of 4. This power law should apply, in the low temperature limit, to the temperature dependence of the energies of all electronic states in semiconductors and insulators.
Collapse
Affiliation(s)
- Manuel Cardona
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
| | | | | |
Collapse
|
9
|
Karaiskaj D, Stotz JAH, Meyer T, Thewalt MLW, Cardona M. Impurity absorption spectroscopy in 28Si: the importance of inhomogeneous isotope broadening. PHYSICAL REVIEW LETTERS 2003; 90:186402. [PMID: 12786030 DOI: 10.1103/physrevlett.90.186402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2003] [Indexed: 05/24/2023]
Abstract
We report high-resolution infrared absorption spectra of the neutral donors phosphorus and lithium, and the neutral acceptor boron, in isotopically pure 28Si crystals. Surprisingly, many of the transitions are much sharper than previously reported in natural Si. In particular, the 2p(0) line of phosphorus in 28Si has a full width at half maximum of only 4.2 microeV, about 5 times less than the narrowest 2p(0) line previously reported for natural Si, making it the narrowest shallow impurity transition yet observed. The widely held assumptions that the impurity transitions previously reported in high quality samples of natural Si revealed the true, homogeneous linewidths, are thus shown to be incorrect. The sharper transitions in 28Si also reveal new substructures in the boron and lithium spectra.
Collapse
Affiliation(s)
- D Karaiskaj
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | |
Collapse
|
10
|
Karaiskaj D, Kirczenow G, Thewalt MLW, Buczko R, Cardona M. Origin of the residual acceptor ground-state splitting in silicon. PHYSICAL REVIEW LETTERS 2003; 90:016404. [PMID: 12570637 DOI: 10.1103/physrevlett.90.016404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2002] [Indexed: 05/24/2023]
Abstract
The residual ground-state splitting of acceptors in high-quality silicon has been studied intensely by different experimental techniques for several decades. Recently, photoluminescence studies of isotopically pure silicon revealed the ground-state splitting to result from the random distribution of isotopes in natural silicon. Here we present a new model that explains these surprising experimental results, and discuss the implications for acceptor ground-state splittings observed in other isotopically mixed semiconductors, as well as for the acceptor ground state in semiconductor alloys.
Collapse
Affiliation(s)
- D Karaiskaj
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | |
Collapse
|
11
|
Karaiskaj D, Thewalt MLW, Ruf T, Cardona M, Konuma M. "Intrinsic" acceptor ground state splitting in silicon: an isotopic effect. PHYSICAL REVIEW LETTERS 2002; 89:016401. [PMID: 12097056 DOI: 10.1103/physrevlett.89.016401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2002] [Indexed: 05/23/2023]
Abstract
One of the oldest open questions in semiconductor physics is the origin of the small splittings of the neutral acceptor ground state in silicon which lead to a distribution of doublet splittings rather than the fourfold-degenerate state of Gamma(8) symmetry expected in the absence of perturbations. Here we show that these acceptor ground state splittings are absent in the photoluminescence spectra of acceptor bound excitons in isotopically purified 28Si, demonstrating conclusively the surprising result that the splittings previously observed in natural Si result from the randomness of the Si isotopic composition.
Collapse
Affiliation(s)
- D Karaiskaj
- Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | | | | | | | | |
Collapse
|
12
|
|
13
|
|