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LATTE Lab in New DOE Energy Frontier Research Center (EFRC)

DOE_imageLATTE Lab is a mem­ber of the new DOE-EFRC cen­ter, Spins and Heat in Nanoscale Elec­tronic Sys­tems (SHINES), led by UC River­side Pro­fes­sor of Physics Jing Shi. The Cen­ter explores the inter­play of spin, charge, and heat to con­trol the trans­port of spin and energy. The four-year research objec­tives include (1) bet­ter under­stand­ing of the effects of spin-orbit cou­pling, includ­ing spin Hall angles and spin-orbit torques (spin Hall torques and Rashba torques); (2) sig­nif­i­cant improve­ment in pure spin cur­rent dri­ven effects, such as magnonic switch­ing, spin-torque oscil­la­tions, and spin See­beck effect through new mate­ri­als and het­erostruc­tures; (3) engi­neer­ing of acoustic/optical phonon, magnon trans­port in nano-structured mate­ri­als via con­trol­ling their dis­per­sions and inter­ac­tions; and (4) explo­ration of the highly cor­re­lated spin super­con­duct­ing con­den­sate for dis­si­pa­tion­less spin and energy trans­port. The pro­posed activ­i­ties will address the Grand Chal­lenge: “How do we con­trol mate­r­ial processes at the level of elec­trons?”, goals iden­ti­fied by the “Basic Research Needs” work­shop, New Sci­ence for a Secure and Sus­tain­able Energy Future, includ­ing the recur­ring theme of “con­trol of pho­ton, elec­tron, spin, phonon, and ion trans­port in mate­ri­als”, and oppor­tu­ni­ties for “con­trol­ling mat­ter and energy at the elec­tronic level”.
Fig­ure by Mahesh Neu­pane and Shan­shan Su.

Reunion of LATTE members in APS March Meeting 2016


Research of LATTE Graduate Students Gen Yin and Yizhou Liu Leads to a $300K NSF Grant on Skyrmions for Information Processing and Storage

skyrmionThis suc­cess­ful three year NSF pro­posal was based on the research results of LATTE grad­u­ate stu­dents Gen Yin and Yizhou Liu work­ing in close col­lab­o­ra­tion with Dr. Jiadong Zang at Johns Hop­kins. A mag­netic skyrmion is a topo­log­i­cally pro­tected, cir­cu­lar, swirling spin tex­ture in which the spins on the periph­ery are polar­ized ver­ti­cally, the cen­tral spin is polar­ized in the oppo­site direc­tion, and, in between, the spins smoothly tran­si­tion between the two oppo­site polar­iza­tions. Skyrmions exist in cer­tain heli­mag­netic mate­ri­als such as the B20 mag­nets in which bro­ken inver­sion sym­me­try gives rise to the Dzyaloshinskii-Moriya inter­ac­tion. The radius of a skyrmion ranges from 3 nm to 100 nm depend­ing on the ratio of the Dzyaloshinskii-Moriya inter­ac­tion and the sym­met­ric Heisen­berg inter­ac­tion. Skyrmion lat­tices and iso­lated skyrmions have been observed in bulk and in thin films, and the elec­tri­cal cur­rent required to move a skyrmion is 4 to 5 orders of mag­ni­tude less than that required to move a more con­ven­tional mag­netic domain wall. Because of the their small size, their sta­bil­ity, the demon­stra­tion of their indi­vid­ual cre­ation and anni­hi­la­tion, and their facile move­ment with low cur­rent, skyrmions are being inves­ti­gated for mag­netic infor­ma­tion stor­age appli­ca­tions. For such appli­ca­tions, an under­stand­ing of the process of skyrmion cre­ation, anni­hi­la­tion, decay, and read­out is required. This project will inves­ti­gate these processes, and it will opti­mize a new method for low-energy skyrmion cre­ation and anni­hi­la­tion using nanosec­ond cur­rent pulses. Read-out using the topo­log­i­cal Hall effect will be ana­lyzed. Four dif­fer­ent archi­tec­tures that exploit a skyrmion state vari­able for infor­ma­tion pro­cess­ing are pro­posed, and open ques­tions con­cern­ing the under­ly­ing phys­i­cal mech­a­nisms and fun­da­men­tal lim­its of the skyrmion sys­tems are iden­ti­fied. These ques­tions will be answered using the­o­ret­i­cal and com­pu­ta­tional meth­ods includ­ing the Landau-Lifshitz-Gilbert equa­tion, ab ini­tio den­sity func­tional the­ory, and the non-equilibrium Green func­tion for­mal­ism. For the Landau-Lifshitz-Gilbert dynam­i­cal sim­u­la­tions of the spin sys­tem, a sto­chas­tic field will be applied to include the effect of ther­mal fluc­tu­a­tions at finite tem­per­a­ture. A new method for low-energy cre­ation and anni­hi­la­tion of skyrmions using a nanosec­ond cur­rent pulse will be opti­mized. The lat­tice ver­sion of the topo­log­i­cal charge will be used to ana­lyze the micro­scopic dynam­i­cal processes. It pro­vides a clear pic­ture of the spin tra­jec­to­ries and ori­en­ta­tions that locally trig­ger a topo­log­i­cal tran­si­tion, it reveals the topo­log­i­cal ori­gin of a skyrmion’s sta­bil­ity at finite tem­per­a­tures, and it sig­nals the exact moment at which a skyrmion is cre­ated or destroyed. A cou­pled Landau-Lifshitz-Gilbert / non-equilibrium Green func­tion approach will be used to inves­ti­gate the use of the topo­log­i­cal Hall volt­age for skyrmion read­out and the inter­ac­tion of spin waves with skyrmions for non-boolean, holo­graphic infor­ma­tion pro­cess­ing. A suc­cess­ful project could lead to new approaches to spin and topo­log­i­cal based com­put­ing. The exploita­tion of low-energy, sta­ble, high-temperature, topo­log­i­cally pro­tected states can result in high-payoff in the tech­nolo­gies of mem­ory and com­pu­ta­tion.
Fig­ure cre­ated by UCR grad­u­ate stu­dent Gen Yin from the sub­mit­ted man­u­script, G. Yin, Y. Li, L. Kong, R. K. Lake, C. L. Chien, and J. Zang, ‘Topo­log­i­cal Charge Analy­sis of Sin­gle Skyrmion Cre­ation with a Nanosec­ond Cur­rent Pulse.’

LATTE Lab receives NSF grant to study 2D Materials

YIG_MoS2_sandwichThe National Sci­ence Foun­da­tion (NSF) ‘s Emerg­ing Fron­tiers in Research and Inno­va­tion (EFRI) pro­gram awarded the  LATTE lab with a multi-year grant.  Over the next four years, the project “Novel Switch­ing Phe­nom­ena in Atomic Het­erostruc­tures for Mul­ti­func­tional Appli­ca­tions” will explore and exploit novel mate­r­ial prop­er­ties of   of van der Waals (vdW) mate­ri­als for elec­tronic device appli­ca­tions. The 2014 awards for Two-dimensional Atomic-layer Research and Engi­neer­ing, were given to nine teams in the U.S. The Uni­ver­sity of Cal­i­for­nia, River­side (UCR) team is led by Alexan­der Balandin with co-PIs Roger Lake, Alexan­der Khi­tun, and Uni­ver­sity of Georgia’s Tina Salguero. The LATTE lab will lead the work in mate­ri­als and device the­ory, mod­el­ing, and sim­u­la­tion. Our lab will explore the elec­tronic, vibra­tional, and mag­netic prop­er­ties of het­ero­lay­ers of 2D mate­ri­als such as the MoS2/YIG/MoS2 “sand­wich” (pic­tured above).

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LATTE Receives Second Prize for 2D Materials Research at the AAAS PAcific Division Conference

Poster by member of LATTE

Mahesh R. Neu­pane pre­sented his research work titled “Effect of Mis­ori­en­ta­tion on the Elec­tronic Prop­er­ties of vdW Mate­ri­als” at the 95th AAAS Pacific Divi­sion Con­fer­ence held on June 16–20, 2014 in the Uni­ver­sity of Cal­i­for­nia, River­side, CA. His research pre­sen­ta­tion in the 2D Mate­ri­als sec­tion was awarded sec­ond prize which includes a cash prize, an award cer­tifi­cate, and a life­time mem­ber­ship of Sigma Xi Soci­ety (a research honor soci­ety). Co-authors were Dar­shana Wick­ra­ma­ratne, Supeng Ge, Gen Yin and Shan­shan Su, all of whom are PhD stu­dents in Prof. R. Lake’s research group. The pre­sen­ta­tion described results from an atom­istic study of the elec­tronic and vibra­tional prop­er­ties of mis­ori­ented, het­erostruc­ture 2D mate­ri­als such as graphene on graphene and graphene on h-BN.

LATTE Receives Best Research Presentation Award at the FENA Review


Masum at FENA Review 2012

Masum at FENA Review 2012

Elec­tri­cal engi­neer­ing PhD can­di­date K. M. Masum Habib received the best research pre­sen­ta­tion award at the com­pe­ti­tion spon­sored by the Defense Advanced Research Projects Agency (DARPA) and Semi­con­duc­tor Research Cor­po­ra­tion (SRC). The event took place Feb. 7 at the Func­tional Engi­neered Nano Archi­tec­ton­ics (FENA) annual review in Los Ange­les. The com­pe­ti­tion fea­tured more than 50 research pre­sen­ta­tions from the top US engi­neer­ing schools such as MIT, UCB, UCLA, UCSB, Stan­ford, Colum­bia Uni­ver­sity, Cal­tech, USC and NCSU. Only one poster was selected from each of the six FENA research themes. Masum Habib won in the Processes and Devices theme. The win­ning pre­sen­ta­tions were selected by rep­re­sen­ta­tives from Intel, Texas Instru­ments, IBM, Raytheon, other indus­try lead­ers and gov­ern­ment orga­ni­za­tions. The award included a Cer­tifi­cate of Achieve­ment and a cash prize. Mr. Habib con­ducts his dis­ser­ta­tion research in Prof. Roger Lake’s Lab­o­ra­tory for Ter­a­hertz and Teras­cale Elec­tron­ics (LATTE).

New Website

LAb­o­ra­tory for Teras­cale and Ter­a­hertz Elec­tron­ics (LATTE) has resigned their web­site recently. It is hosted on LATTE’s own server run­ning on FreeBSD. The web­pages are gen­er­ated by Word­Press and served by Apache webserver.