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Title: Excitonic mass gap in uniaxially strained graphene

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 23; Related Information: CHORUS Timestamp: 2017-06-13 22:12:57; Journal ID: ISSN 2469-9950
American Physical Society
Country of Publication:
United States

Citation Formats

Sharma, Anand, Kotov, Valeri N., and Castro Neto, Antonio H. Excitonic mass gap in uniaxially strained graphene. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.235124.
Sharma, Anand, Kotov, Valeri N., & Castro Neto, Antonio H. Excitonic mass gap in uniaxially strained graphene. United States. doi:10.1103/PhysRevB.95.235124.
Sharma, Anand, Kotov, Valeri N., and Castro Neto, Antonio H. 2017. "Excitonic mass gap in uniaxially strained graphene". United States. doi:10.1103/PhysRevB.95.235124.
title = {Excitonic mass gap in uniaxially strained graphene},
author = {Sharma, Anand and Kotov, Valeri N. and Castro Neto, Antonio H.},
abstractNote = {},
doi = {10.1103/PhysRevB.95.235124},
journal = {Physical Review B},
number = 23,
volume = 95,
place = {United States},
year = 2017,
month = 6

Journal Article:
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Publisher's Accepted Manuscript

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  • The effect of strain on the Landau levels (LLs) spectra in graphene is studied, using an effective Dirac-like Hamiltonian which includes the distortion in the Dirac cones, anisotropy and spatial-dependence of the Fermi velocity induced by the lattice change through a renormalized linear momentum. We propose a geometrical approach to obtain the electron’s wave-function and the LLs in graphene from the Sturm–Liouville theory, using the minimal substitution method. The coefficients of the renormalized linear momentum are fitted to the energy bands, which are obtained from a Density Functional Theory (DFT) calculation. In particular, we evaluate the case of Dirac conesmore » with an ellipsoidal transversal section resulting from uniaxially strained graphene along the Arm-Chair (AC) and Zig-Zag (ZZ) directions. We found that uniaxial strain in graphene induces a contraction of the LLs spectra for both strain directions. Also, is evaluated the contribution of the tilting of Dirac cone axis resulting from the uniaxial deformations to the contraction of the LLs spectra. - Highlights: • The LLs in uniaxially strained graphene are found using a geometrical approach. • The energy of the LLs in function of the Dirac cone deformation is presented. • We found that uniaxial strain in graphene induces a contraction of the LLs spectra. • Contraction in LLs spectra depends on the geometrical parameters of the Dirac cone.« less
  • The way that emission lines from bound and free excitons in CdTe shift, split, and change in intensity under uniaxial strain have been investigated theoretically and experimentally. The nonlinear shift observed in the energy positions of peaks due to acceptor-bound excitons is caused by strong spin-spin interaction in the system of two heavy holes. A nonmonotonic dependence and abrupt quenching of the intensity of emission from acceptor-bound excitons in the high-strain regime (pressures P>1 kbar) with a simultaneous buildup in the free-exciton emission line has been observed. The theoretical model considers two basic mechanisms for recombination-radiative and Auger recombination. Themore » results which were obtained can be used to identify types of defects in CdTe, and to determine local mechanical stresses in CdTe-based heterostructures. 17 refs., 5 figs.« less
  • The nonlinear optical properties of a new class of strained-layer superlattices (intrinsic Stark effect superlattices) have been investigated. Specifically, we have compared the nonlinear transmission of Ga{sub 1{minus}{ital x}}In{sub {ital x}}As-GaAs strained-layer superlattices grown along the (211) axis to identical superlattices grown along the (100) axis, and found that the optical nonlinearity in the (211) sample is about one order of magnitude greater than in the (100) sample. A blue shift of the exciton resonance and an increase in the exciton absorption strength in the (211) sample with increasing light intensity was observed (attributed to screening of the intrinsic Starkmore » effect fields by photogenerated carriers), resulting in the stronger optical nonlinearity. The maximum of the nonlinear absorption index, {vert bar}{alpha}{sub 2}{vert bar}, in the (211) sample was 54 cm/W ({vert bar}Im {chi}{sup 3}{vert bar}=0.33 esu) whereas in the (100) sample the maximum of {vert bar}{alpha}{sub 2}{vert bar} was 6.9 cm/W ({vert bar}Im {chi}{sup 3}{vert bar}=0.042 esu). The measured carrier recovery time in both samples was 2 ns.« less
  • Excitonic transitions in metalorganic vapor phase epitaxially grown In[sub [ital x]]Ga[sub 1[minus][ital x]]P/In[sub 0.48](Al[sub 0.7]Ga[sub 0.3])[sub 0.52]P strained single quantum-well structures are characterized using low-temperature photoluminescence and photoluminescence excitation (PLE) spectroscopies. The structures consist of several uncoupled quantum wells with thicknesses between 1.2 and 11.3 nm, and compositions [ital x] of 0.48 (nominally lattice matched) and 0.56 ([similar to]0.6% biaxial compressive strain). The photoluminescence spectra exhibit intense peaks over the wavelength range 550--650 nm, with linewidths between 7 and 23 meV depending on the well thickness. The PLE spectra reveal strong heavy-hole and light-hole transitions, as well as higher-order ([italmore » n]=2) transitions in the thicker wells. The heavy-hole/light-hole splitting shows little dependence on well thickness in the strained structures, indicating a relatively large conduction band offset of [Delta][ital E][sub [ital C]][similar to]0.75[Delta][ital E][sub [ital G]].« less
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