New half-light half-mat­ter par­ti­cles may hold the key to a com­put­ing rev­o­lu­tion

Tehran Times - - SCIENCE -

Sci­en­tists have dis­cov­ered new par­ti­cles that could lie at the heart of a fu­ture tech­no­log­i­cal rev­o­lu­tion based on pho­tonic cir­cuitry, lead­ing to su­per­fast, light-based com­put­ing.

Cur­rent com­put­ing tech­nol­ogy is based on elec­tron­ics, where elec­trons are used to en­code and trans­port in­for­ma­tion.

Due to some fun­da­men­tal lim­i­ta­tions, such as en­ergy-loss through re­sis­tive heat­ing, it is ex­pected that elec­trons will even­tu­ally need to be re­placed by pho­tons, lead­ing to fu­tur­is­tic light-based com­put­ers that are much faster and more ef­fi­cient than cur­rent elec­tronic ones.

Physi­cists at the Univer­sity of Ex­eter have taken an im­por­tant step to­wards this goal, as they have dis­cov­ered new half-light half-mat­ter par­ti­cles that in­herit some of the re­mark­able fea­tures of graphene.

This dis­cov­ery opens the door for the de­vel­op­ment of pho­tonic cir­cuitry us­ing these al­ter­na­tive par­ti­cles, known as mass­less Dirac po­lari­tons, to trans­port in­for­ma­tion rather than elec­trons.

Dirac po­lari­tons emerge in hon­ey­comb meta­sur­faces, which are ul­tra-thin ma­te­ri­als that are en­gi­neered to have struc­ture on the nanoscale, much smaller than the wave­length of light.

A unique fea­ture of Dirac par­ti­cles is that they mimic rel­a­tivis­tic par­ti­cles with no mass, al­low­ing them to travel very ef­fi­ciently. This fact makes graphene one of the most con­duc­tive ma­te­ri­als known to man.

How­ever, de­spite their ex­tra­or­di­nary prop­er­ties, it is very dif­fi­cult to con­trol them. For ex­am­ple, in graphene it is im­pos­si­ble to switch on/off elec­tri­cal cur­rents us­ing sim­ple elec­tri­cal po­ten­tial, thus hin­der­ing the po­ten­tial im­ple­men­ta­tion of graphene in elec­tronic de­vices.

This fun­da­men­tal draw­back—the lack of ten­abil­ity — has been suc­cess­fully over­come in a unique way by the physi­cists at the Univer­sity of Ex­eter.

Char­lie-Ray Mann, the lead au­thor of the pa­per pub­lished in Na­ture Com­mu­ni­ca­tions, ex­plains: “For graphene, one usu­ally has to mod­ify the hon­ey­comb lat­tice to change its prop­er­ties, for ex­am­ple by strain­ing the hon­ey­comb lat­tice which is ex­tremely chal­leng­ing to do con­trol­lably.”

Hy­brid par­ti­cles

The “key dif­fer­ence here is that the Dirac po­lari­tons are hy­brid par­ti­cles, a mix­ture of light and mat­ter com­po­nents. It is this hy­brid na­ture that presents us with a unique way to tune their fun­da­men­tal prop­er­ties, by ma­nip­u­lat­ing only their light-com­po­nent, some­thing that is im­pos­si­ble to do in graphene.”

The re­searchers show that by em­bed­ding the hon­ey­comb meta­sur­face be­tween two re­flect­ing mir­rors and chang­ing the dis­tance be­tween them, one can tune the fun­da­men­tal prop­er­ties of the Dirac po­lari­tons in a sim­ple, con­trol­lable and re­versible way.

“Our work has cru­cial im­pli­ca­tions for the re­search fields of pho­ton­ics and of Dirac par­ti­cles,” adds Dr. Eros Mar­i­ani, prin­ci­pal in­ves­ti­ga­tor on the study.

“We have shown the abil­ity to slow down or even stop the Dirac par­ti­cles, and mod­ify their in­ter­nal struc­ture, their chi­ral­ity, in tech­ni­cal terms, which is im­pos­si­ble to do in graphene it­self”

The “achieve­ments of our work will con­sti­tute a key step along the pho­tonic cir­cuitry rev­o­lu­tion.”

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