Acoustic metamaterials in nanoscale Dr. Ari Salmi www.helsinki.fi/yliopisto 12.2.2014 1
Revisit to resonances Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 2
How does the fullerene resonance work in practice? The fullerenes are either in a gas or a liquid Detection via Brillouin spectroscopy? 5 Å 12.2.2014 3
Revisit to acoustic AFM Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 4
How does one hold the molecules in place for nc-afm? The molecules adsorb to Cu(111) (Lagoute et al., Phys Rev B 2004) 5 Å 12.2.2014 5
How does one know that the tip has been functionalized? Bartels et al., PRL 1998 Apply a voltage to the tip the CO molecule jumps from the Cu(111) surface Attachment detected as a change of the STM image 5 Å 12.2.2014 6
Phonons and heat Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 7
Physics: Phonons and heat A very good paper by Maldovan, Nature 2013 (November) 12.2.2014 8
Visualization of phonons Check out and play with http://www.phonon.fc.pl/index.php For an explanation of the first Brillouin zone of a fcc crystal, see http://lamp.tugraz.ac.at/~hadley/ss1/bzones/fcc.php 12.2.2014 9
Physics: Phonons and heat What is heat? Heat is phonons at T = 0 K, no phonons exist Phonons of all allowed frequencies (from the dispersion relation for the system at hand) are excited Density of states at a higher temperature, higher frequencies dominate 12.2.2014 10
Physics: Phonons and heat Phonon-phonon scattering Normal scattering conserves phonon momentum Umklapp changes the momentum frequency changes 12.2.2014 11
Acoustic metamaterials Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 12
Acoustic metamaterials Man-made materials Idea: Control, direct or manipulate sound waves 5 Å 12.2.2014 13 http://www.electronics-lab.com/blog/wp-content/uploads/2011/01/nl110110-foto.jpg
First acoustic metamaterial: Sonic crystals Liu et al., Science 2000 1 cm diameter lead balls coated with 2.5 mm of silicone rubber These balls stacked in a 8x8 lattice 5 Å 12.2.2014 14
First acoustic metamaterial The transmission of sound featured bandgaps Certain frequency bands where sound does not propagate Negative effective elastic modulus! 5 Å 12.2.2014 15
Double-negative acoustic metamaterials Li et al., Phys. Rev. E, 2004 and Ding et al., PRL 2007 (theoretical) In a double-negative material, both the bulk modulus and density are negative Poynting vector and wave vector point in different directions What does that mean in practice? Material that Expands in compression (negative K) Moves to the left when pushed to the right (negative density) 5 Å 12.2.2014 16
Double-negative acoustic metamaterials Experimental: Lee et al., PRL 2010 Showed double negativity Negative phase velocity 5 Å 12.2.2014 17
Material based sound focusing Zhang et al., PRL 2009 Based on a double-negative material Left half: Positive n, Right half: negative n focusing of the wave from a point source 5 Å 12.2.2014 18
Acoustic diodes Diode = directional dependence of current In electric diodes, electric current Acoustic diodes sound propagates in only one direction 12.2.2014 19
Acoustic diodes in practice Liang et al., Nature materials 2010 Used a superlattice structure Fancy word for a water-glass laminate structure (1.4 mm thickness of layers) 12.2.2014 20
Acoustic diodes in practice Boechler et al., Nature materials 2011 Adjustable diode 1 cm steel spheres 12.2.2014 21
Acoustic diodes for surface waves Jia et al., Applied Physics Letters 2013 (April) Lamb wave acoustic diode Patterned steel plate 12.2.2014 22
Acoustic cloaking Zhang et al, PRL 2011 Acoustic cloak = a device that allows cloaking of an object from sound waves A metamaterial construct capable of acoustic cloaking with broadband frequencies 12.2.2014 23
Acoustic cloaking Quite good results already Not a perfect cloak, but close 12.2.2014 24
Acoustic metamaterials in nanoscale Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 25
Phononic crystals Towards nanoscale: sonic crystals (phononic crystals) 12.2.2014 26
Hypersonic crystals Gorishnyy et al., PRL 2005 Sonic crystals: ω g = 10 2-10 3 Hz Ultrasonic crystals: ω g = 10 4-10 6 Hz Hypersonic crystals: ω g = 10 9-10 12 Hz Build 2D hypersonic crystals with interference lithography Epoxy on glass 12.2.2014 27
Hypersonic crystals Characterize phonon propagation with Brillouin light scattering Probes only phonons propagating in-plane Longitudinal phonons in glass (1) and epoxy (2) Propagating phonons in the phononic crystal (3 and 4) 12.2.2014 28
Hypersonic crystals Also, detection of the phonon mode map Semi-bandgaps (mixed modes present) 12.2.2014 29
Hypersonic crystals Cheng et al., Nature Materials, 2006 Polystyrene opal structure embedded in oil Probed by Brillouin spectroscopy Features a band gap! 12.2.2014 30
Hypersonic crystals The band gap is tunable by adjusting the particle diameter 12.2.2014 31
Phononic crystals Wen et al., Applied Physics Letters 2010 Semiconductor quantum dots 12.2.2014 32
Phononic crystals Simulations predict two mini band gaps at 340 GHz and at 700 GHz 12.2.2014 33
Phononic crystals Experiments: Pump-probe measurement of the excited coherent phonons Ti:Sa @ 780 nm (150 fs) 12.2.2014 34
Phononic crystals First band gap clearly visible as an increase in the received reflected amplitude Not visible in a random Q-dot structure 12.2.2014 35
Sound-light interaction: Modulation of photonic crystals by GHz phonons Fuhrmann et al., Nature Photonics 2011 Modulate a photonic grating by a traveling SAW Q-dots on a GaAs layer that are excited 12.2.2014 36
Sound-light interaction: Modulation of photonic crystals by GHz phonons Light emission from the q-dots (resonance cavities) is changed by the change of dimensions 12.2.2014 37
Phononic crystals Maldovan, PRL, 2013 Thermocrystals = sonic crystals for phonons 12.2.2014 38
Phononic crystals Maldovan, PRL, 2013 Suggestions for future phononic devices 12.2.2014 39
Phonon diodes Phonons are practically heat Phononic diodes are thermal diodes! Chang et al., Science 2006 SWCNT-based thermal diode Coated with C 9 H 16 Pt 12.2.2014 40
Phonon diodes Ordinary waves: Reciprocity no rectification Soliton waves in CNT s Korteweg-de Varies equation for reflection fraction of masses determines reflection! 12.2.2014 41
Phonon diodes Wang et al., Nano Letters 6.1.2014 Asymmetric graphene nanoribbons act as thermal diodes 12.2.2014 42
Phonon diodes Also, other diode types predicted by simulations 12.2.2014 43
Optomechanical crystals Eichenfield et al., Nature 2009 Idea: combine a phononic and a photonic crystal optomechanical crystal Strongly couple light and sound 2 GHz phonons and 200 THz photons Si nanobeam 12.2.2014 44
Optomechanical crystals Acoustic modes in the structure 12.2.2014 45
Optomechanical crystals Sound and light co-localized! Localization by small defects 12.2.2014 46
Optomechanical crystals Amplification of the acoustic breathing mode by light 12.2.2014 47
Electromagnetically induced transparency Coherent optical nonlinearity which makes a medium transparent over a narrow spectral range within an absorption line rapid change of index of refraction 12.2.2014 48
Optomechanical crystals - applications Safavi-Neieni et al., Nature 2011 created EIT with an optomechanical crystal Superluminal light and slow light (v = 40 m/s) 12.2.2014 49
Optomechanical crystals - applications Chan et al., Nature 2011 Super efficient cooling via light-sound interaction Down to quantum ground state (0.85 phonons per state) 12.2.2014 50
Phonon cloaks Narayana et al., PRL 2012 Heat flux (phonons) between a hot and a cold bath Thermal shielding (b), flux focusing (c) and inversion (d) 12.2.2014 51
Phonon cloaks Phonon shielding Copper Polyurethane Metamaterial 12.2.2014 52
Phonon cloaks Phonon focusing 12.2.2014 53
Phonon cloaks Heat flux inversion 12.2.2014 54
Take-home Matemaattis-luonnontieteellinen tiedekunta / Henkilön nimi / Esityksen nimi www.helsinki.fi/yliopisto 12.2.2014 55
Take-home: Acoustic metamaterials in nanoscale Ultra-high frequency: Rectification (diodes) Cloaking Band gaps 12.2.2014 56
Optomechanical crystals - applications Safavi-Neieni et al., Nature 2011 Electromagnetically induced transparency a/b = photon/phonon annihilation/creation quanta Control beam 12.2.2014 57