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　　北京(jing)大學物(wu)理學院(yuan)量(liang)子(zi)(zi)(zi)(zi)(zi)(zi)材(cai)料(liao)科學中(zhong)心和(he)電(dian)(dian)子(zi)(zi)(zi)(zi)(zi)(zi)顯(xian)微鏡(jing)(jing)(jing)實(shi)驗室高鵬、陳基、王恩(en)哥院(yuan)士課題組(zu)等(deng)(deng)與北京(jing)大學材(cai)料(liao)科學與工(gong)(gong)程(cheng)學院(yuan)劉(liu)磊等(deng)(deng)課題組(zu)合(he)(he)作(zuo)，首次實(shi)現了在(zai)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)尺(chi)度(du)上對同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)的(de)研究。原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)尺(chi)度(du)上探(tan)(tan)測(ce)同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)極具挑戰，目(mu)前(qian)(qian)具有原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)分辨能力的(de)實(shi)驗技(ji)術(shu)只有掃描探(tan)(tan)針顯(xian)微鏡(jing)(jing)(jing)和(he)透射(she)電(dian)(dian)子(zi)(zi)(zi)(zi)(zi)(zi)顯(xian)微鏡(jing)(jing)(jing)，而前(qian)(qian)者(zhe)只能探(tan)(tan)測(ce)表(biao)面(mian)(mian)，后者(zhe)雖(sui)然(ran)可以(yi)探(tan)(tan)測(ce)包(bao)埋的(de)界面(mian)(mian)，但是所(suo)有的(de)電(dian)(dian)鏡(jing)(jing)(jing)成像(xiang)和(he)電(dian)(dian)子(zi)(zi)(zi)(zi)(zi)(zi)衍(yan)射(she)技(ji)術(shu)都(dou)只對質子(zi)(zi)(zi)(zi)(zi)(zi)數(shu)目(mu)敏(min)感(gan)而對中(zhong)子(zi)(zi)(zi)(zi)(zi)(zi)不敏(min)感(gan)，因此無法(fa)識別同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)。北大團隊(dui)利(li)用電(dian)(dian)鏡(jing)(jing)(jing)的(de)非彈(dan)性散(san)射(she)技(ji)術(shu)，根據同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)聲(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)能量(liang)的(de)差異，首次在(zai)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)尺(chi)度(du)上實(shi)現了對同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)的(de)識別和(he)探(tan)(tan)測(ce)，展(zhan)示了電(dian)(dian)鏡(jing)(jing)(jing)在(zai)研究原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)核量(liang)子(zi)(zi)(zi)(zi)(zi)(zi)效應(ying)方面(mian)(mian)的(de)潛力。他們構筑(zhu)了純化(hua)的(de)氮化(hua)硼(peng)h-10BN和(he)h-11BN同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)范(fan)德華界面(mian)(mian)，利(li)用掃描透射(she)電(dian)(dian)子(zi)(zi)(zi)(zi)(zi)(zi)顯(xian)微鏡(jing)(jing)(jing)的(de)電(dian)(dian)子(zi)(zi)(zi)(zi)(zi)(zi)能量(liang)損失譜技(ji)術(shu)，在(zai)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)分辨下測(ce)量(liang)了同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)附近的(de)聲(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)模式，觀察到由(you)電(dian)(dian)聲(sheng)耦合(he)(he)作(zuo)用導(dao)致的(de)布(bu)里淵區中(zhong)心和(he)邊界的(de)聲(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)在(zai)同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)上迥異的(de)過渡區域(yu)長度(du)。由(you)于自(zi)然(ran)界中(zhong)絕大部分物(wu)質都(dou)是同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)混合(he)(he)物(wu)，該工(gong)(gong)作(zuo)表(biao)明同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)之間會產生新的(de)界面(mian)(mian)效應(ying)從而改變(bian)局域(yu)的(de)物(wu)理性質，為理解天然(ran)材(cai)料(liao)的(de)物(wu)性提供(gong)了新的(de)視角。該研究成果以(yi)《同(tong)(tong)(tong)(tong)(tong)位(wei)(wei)(wei)素(su)(su)(su)(su)(su)(su)界面(mian)(mian)上的(de)聲(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)轉變(bian)》(Phonon transition across an isotopic interface)為題，于2023年4月26日(ri)發(fa)表(biao)在(zai)《自(zi)然(ran)·通(tong)訊》(Nature Communications 2023, 14, 2382)。

　　同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)指的(de)(de)(de)(de)(de)是(shi)(shi)(shi)(shi)(shi)具(ju)有(you)相(xiang)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)質(zhi)(zhi)(zhi)子(zi)(zi)(zi)(zi)(zi)數(shu)(shu)但(dan)(dan)不(bu)(bu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)中(zhong)子(zi)(zi)(zi)(zi)(zi)數(shu)(shu)的(de)(de)(de)(de)(de)元(yuan)素(su)(su)(su)。同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)具(ju)有(you)不(bu)(bu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)的(de)(de)(de)(de)(de)原(yuan)子(zi)(zi)(zi)(zi)(zi)質(zhi)(zhi)(zhi)量(liang)(liang)(liang)(liang)(liang)，因(yin)此(ci)(ci)很(hen)(hen)多與核(he)相(xiang)關的(de)(de)(de)(de)(de)物(wu)(wu)理化(hua)(hua)學(xue)性(xing)(xing)質(zhi)(zhi)(zhi)會不(bu)(bu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)，例如(ru)核(he)反應、彈(dan)性(xing)(xing)模量(liang)(liang)(liang)(liang)(liang)、聲(sheng)子(zi)(zi)(zi)(zi)(zi)熱導(dao)(dao)(dao)率(lv)等(deng)。但(dan)(dan)由于(yu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)具(ju)有(you)相(xiang)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)數(shu)(shu)目(mu)，因(yin)此(ci)(ci)它們(men)很(hen)(hen)多的(de)(de)(de)(de)(de)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)結(jie)構性(xing)(xing)質(zhi)(zhi)(zhi)是(shi)(shi)(shi)(shi)(shi)類似的(de)(de)(de)(de)(de)，這(zhe)使得同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)技(ji)(ji)(ji)術(shu)被廣泛(fan)用(yong)作分(fen)(fen)子(zi)(zi)(zi)(zi)(zi)標(biao)記(ji)、化(hua)(hua)學(xue)反應、輻射(she)(she)定年中(zhong)的(de)(de)(de)(de)(de)示(shi)蹤劑。最近的(de)(de)(de)(de)(de)研究還報告了同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)對(dui)化(hua)(hua)學(xue)/電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)性(xing)(xing)質(zhi)(zhi)(zhi)的(de)(de)(de)(de)(de)影(ying)響，包(bao)括超導(dao)(dao)(dao)電(dian)(dian)(dian)性(xing)(xing)、透(tou)(tou)(tou)射(she)(she)率(lv)和(he)光學(xue)帶隙等(deng)。這(zhe)些現象為利用(yong)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)進行功(gong)能(neng)(neng)(neng)設(she)計打(da)開了一扇(shan)新的(de)(de)(de)(de)(de)大門，但(dan)(dan)也引起(qi)了一些新的(de)(de)(de)(de)(de)思考：天(tian)(tian)然(ran)(ran)(ran)材(cai)料(liao)(liao)通常是(shi)(shi)(shi)(shi)(shi)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)的(de)(de)(de)(de)(de)混合物(wu)(wu)，那么(me)可能(neng)(neng)(neng)存在(zai)(zai)(zai)(zai)的(de)(de)(de)(de)(de)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)是(shi)(shi)(shi)(shi)(shi)否會出現新的(de)(de)(de)(de)(de)物(wu)(wu)理化(hua)(hua)學(xue)性(xing)(xing)質(zhi)(zhi)(zhi)?例如(ru)，與天(tian)(tian)然(ran)(ran)(ran)材(cai)料(liao)(liao)相(xiang)比，同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)純化(hua)(hua)的(de)(de)(de)(de)(de)材(cai)料(liao)(liao)的(de)(de)(de)(de)(de)熱導(dao)(dao)(dao)率(lv)得到了極大增(zeng)強。對(dui)于(yu)該現象的(de)(de)(de)(de)(de)公認解釋是(shi)(shi)(shi)(shi)(shi)：天(tian)(tian)然(ran)(ran)(ran)材(cai)料(liao)(liao)中(zhong)的(de)(de)(de)(de)(de)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)質(zhi)(zhi)(zhi)量(liang)(liang)(liang)(liang)(liang)無(wu)(wu)序引起(qi)了聲(sheng)子(zi)(zi)(zi)(zi)(zi)散射(she)(she)，降低了聲(sheng)子(zi)(zi)(zi)(zi)(zi)平均自由程，導(dao)(dao)(dao)致熱導(dao)(dao)(dao)率(lv)大幅降低。然(ran)(ran)(ran)而在(zai)(zai)(zai)(zai)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)不(bu)(bu)均勻(yun)(yun)分(fen)(fen)布的(de)(de)(de)(de)(de)情況下，天(tian)(tian)然(ran)(ran)(ran)材(cai)料(liao)(liao)中(zhong)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)的(de)(de)(de)(de)(de)存在(zai)(zai)(zai)(zai)使其類似于(yu)“超晶格”的(de)(de)(de)(de)(de)情況，而界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)一般會具(ju)有(you)局域(yu)的(de)(de)(de)(de)(de)不(bu)(bu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)于(yu)體態的(de)(de)(de)(de)(de)導(dao)(dao)(dao)熱能(neng)(neng)(neng)力。在(zai)(zai)(zai)(zai)這(zhe)種情況下，熱導(dao)(dao)(dao)等(deng)物(wu)(wu)理化(hua)(hua)學(xue)性(xing)(xing)質(zhi)(zhi)(zhi)在(zai)(zai)(zai)(zai)直覺上(shang)應該與完全均勻(yun)(yun)的(de)(de)(de)(de)(de)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)混合物(wu)(wu)有(you)所不(bu)(bu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)。盡管如(ru)此(ci)(ci)，關于(yu)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)及其可能(neng)(neng)(neng)存在(zai)(zai)(zai)(zai)的(de)(de)(de)(de)(de)物(wu)(wu)性(xing)(xing)影(ying)響在(zai)(zai)(zai)(zai)以(yi)前(qian)很(hen)(hen)少被討論，在(zai)(zai)(zai)(zai)很(hen)(hen)大程度上(shang)都是(shi)(shi)(shi)(shi)(shi)未知的(de)(de)(de)(de)(de)，這(zhe)主(zhu)要是(shi)(shi)(shi)(shi)(shi)因(yin)為在(zai)(zai)(zai)(zai)原(yuan)子(zi)(zi)(zi)(zi)(zi)尺度上(shang)識(shi)別同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)存在(zai)(zai)(zai)(zai)很(hen)(hen)大挑戰，更不(bu)(bu)用(yong)說(shuo)在(zai)(zai)(zai)(zai)原(yuan)子(zi)(zi)(zi)(zi)(zi)尺度上(shang)測(ce)(ce)量(liang)(liang)(liang)(liang)(liang)其界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)的(de)(de)(de)(de)(de)物(wu)(wu)理化(hua)(hua)學(xue)性(xing)(xing)質(zhi)(zhi)(zhi)。比如(ru)，常用(yong)的(de)(de)(de)(de)(de)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)識(shi)別方法是(shi)(shi)(shi)(shi)(shi)基(ji)于(yu)拉曼、紅外吸(xi)收(shou)光譜(pu)(pu)等(deng)振動(dong)光譜(pu)(pu)技(ji)(ji)(ji)術(shu)，它們(men)具(ju)有(you)很(hen)(hen)高(gao)的(de)(de)(de)(de)(de)能(neng)(neng)(neng)量(liang)(liang)(liang)(liang)(liang)分(fen)(fen)辨(bian)率(lv)，能(neng)(neng)(neng)夠根據探(tan)(tan)測(ce)(ce)的(de)(de)(de)(de)(de)聲(sheng)子(zi)(zi)(zi)(zi)(zi)能(neng)(neng)(neng)量(liang)(liang)(liang)(liang)(liang)差異來(lai)區分(fen)(fen)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)，但(dan)(dan)通常它們(men)的(de)(de)(de)(de)(de)空(kong)(kong)(kong)間(jian)分(fen)(fen)辨(bian)率(lv)有(you)限。盡管近年來(lai)基(ji)于(yu)針尖增(zeng)強拉曼光譜(pu)(pu)和(he)掃(sao)描近場光學(xue)顯微(wei)(wei)(wei)鏡(jing)已(yi)經(jing)顯著提高(gao)了它們(men)的(de)(de)(de)(de)(de)空(kong)(kong)(kong)間(jian)分(fen)(fen)辨(bian)率(lv)，這(zhe)些技(ji)(ji)(ji)術(shu)依然(ran)(ran)(ran)難以(yi)解析原(yuan)子(zi)(zi)(zi)(zi)(zi)結(jie)構，也無(wu)(wu)法探(tan)(tan)測(ce)(ce)布里(li)淵區邊界(jie)(jie)處(chu)的(de)(de)(de)(de)(de)高(gao)動(dong)量(liang)(liang)(liang)(liang)(liang)聲(sheng)子(zi)(zi)(zi)(zi)(zi)。實際上(shang)目(mu)前(qian)具(ju)有(you)原(yuan)子(zi)(zi)(zi)(zi)(zi)分(fen)(fen)辨(bian)能(neng)(neng)(neng)力的(de)(de)(de)(de)(de)實空(kong)(kong)(kong)間(jian)實驗探(tan)(tan)測(ce)(ce)技(ji)(ji)(ji)術(shu)只(zhi)有(you)掃(sao)描探(tan)(tan)針顯微(wei)(wei)(wei)鏡(jing)和(he)透(tou)(tou)(tou)射(she)(she)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)顯微(wei)(wei)(wei)鏡(jing)，而掃(sao)描探(tan)(tan)針顯微(wei)(wei)(wei)鏡(jing)技(ji)(ji)(ji)術(shu)只(zhi)能(neng)(neng)(neng)探(tan)(tan)測(ce)(ce)表面(mian)(mian)(mian)(mian)(mian)，雖然(ran)(ran)(ran)透(tou)(tou)(tou)射(she)(she)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)顯微(wei)(wei)(wei)鏡(jing)可以(yi)探(tan)(tan)測(ce)(ce)包(bao)埋(mai)在(zai)(zai)(zai)(zai)內部的(de)(de)(de)(de)(de)界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)，但(dan)(dan)是(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)鏡(jing)的(de)(de)(de)(de)(de)成像和(he)衍射(she)(she)都只(zhi)對(dui)質(zhi)(zhi)(zhi)子(zi)(zi)(zi)(zi)(zi)敏感而對(dui)中(zhong)子(zi)(zi)(zi)(zi)(zi)不(bu)(bu)敏感，因(yin)此(ci)(ci)無(wu)(wu)法區分(fen)(fen)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)。近年來(lai)，基(ji)于(yu)掃(sao)描透(tou)(tou)(tou)射(she)(she)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)顯微(wei)(wei)(wei)鏡(jing)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)能(neng)(neng)(neng)量(liang)(liang)(liang)(liang)(liang)損(sun)失譜(pu)(pu)得到迅速發展(zhan)，為聲(sheng)子(zi)(zi)(zi)(zi)(zi)測(ce)(ce)量(liang)(liang)(liang)(liang)(liang)提供了新的(de)(de)(de)(de)(de)技(ji)(ji)(ji)術(shu)路線。其中(zhong)，北京大學(xue)高(gao)鵬課題(ti)組近年來(lai)發展(zhan)了“四維電(dian)(dian)(dian)子(zi)(zi)(zi)(zi)(zi)能(neng)(neng)(neng)量(liang)(liang)(liang)(liang)(liang)損(sun)失譜(pu)(pu)測(ce)(ce)量(liang)(liang)(liang)(liang)(liang)技(ji)(ji)(ji)術(shu)”，克服了傳統譜(pu)(pu)學(xue)無(wu)(wu)法同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)時具(ju)備高(gao)動(dong)量(liang)(liang)(liang)(liang)(liang)分(fen)(fen)辨(bian)和(he)納米級空(kong)(kong)(kong)間(jian)分(fen)(fen)辨(bian)的(de)(de)(de)(de)(de)缺點，為原(yuan)子(zi)(zi)(zi)(zi)(zi)尺度上(shang)探(tan)(tan)測(ce)(ce)同(tong)(tong)(tong)(tong)(tong)(tong)(tong)(tong)位(wei)(wei)素(su)(su)(su)界(jie)(jie)面(mian)(mian)(mian)(mian)(mian)物(wu)(wu)性(xing)(xing)提供了可能(neng)(neng)(neng)。

　　在(zai)(zai)(zai)(zai)最近發(fa)表的(de)(de)(de)(de)(de)(de)(de)工作里(li)，北大(da)團隊(dui)制備了(le)(le)高純度的(de)(de)(de)(de)(de)(de)(de)h-10BN和(he)h-11BN材料(liao)，并且堆垛得到人工的(de)(de)(de)(de)(de)(de)(de)同(tong)(tong)位(wei)素(su)范德(de)華界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)。他們(men)利用h-BN材料(liao)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)能帶的(de)(de)(de)(de)(de)(de)(de)特點(dian)，將(jiang)電(dian)子(zi)(zi)(zi)(zi)(zi)(zi)能量(liang)(liang)(liang)損失譜(pu)的(de)(de)(de)(de)(de)(de)(de)空間(jian)分(fen)辨率(lv)設置(zhi)在(zai)(zai)(zai)(zai)原(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)分(fen)辨尺度，同(tong)(tong)時又(you)具備一定(ding)(ding)的(de)(de)(de)(de)(de)(de)(de)區(qu)(qu)分(fen)布(bu)里(li)淵(yuan)(yuan)區(qu)(qu)中(zhong)心(xin)(xin)(xin)和(he)布(bu)里(li)淵(yuan)(yuan)區(qu)(qu)邊(bian)界(jie)(jie)(jie)(jie)(jie)(jie)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)的(de)(de)(de)(de)(de)(de)(de)能力，從(cong)而測量(liang)(liang)(liang)同(tong)(tong)位(wei)素(su)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)處的(de)(de)(de)(de)(de)(de)(de)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)行(xing)為(wei)(wei)(wei)(wei)。他們(men)發(fa)現界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)處的(de)(de)(de)(de)(de)(de)(de)面(mian)(mian)(mian)(mian)外(wai)振(zhen)(zhen)動(dong)(dong)的(de)(de)(de)(de)(de)(de)(de)光學(xue)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)模式(稱為(wei)(wei)(wei)(wei)ZO)在(zai)(zai)(zai)(zai)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)處是(shi)(shi)逐漸過(guo)渡的(de)(de)(de)(de)(de)(de)(de)，存在(zai)(zai)(zai)(zai)明(ming)顯的(de)(de)(de)(de)(de)(de)(de)離域(yu)(yu)(yu)行(xing)為(wei)(wei)(wei)(wei)。此(ci)外(wai)，其離域(yu)(yu)(yu)程度依(yi)賴(lai)于(yu)(yu)ZO模的(de)(de)(de)(de)(de)(de)(de)動(dong)(dong)量(liang)(liang)(liang)轉移(yi)(yi)，即在(zai)(zai)(zai)(zai)小動(dong)(dong)量(liang)(liang)(liang)轉移(yi)(yi)下(對(dui)應(ying)于(yu)(yu)布(bu)里(li)淵(yuan)(yuan)區(qu)(qu)中(zhong)心(xin)(xin)(xin)的(de)(de)(de)(de)(de)(de)(de)ZO)離域(yu)(yu)(yu)度大(da)約(yue)為(wei)(wei)(wei)(wei)3.34納米(mi)，而在(zai)(zai)(zai)(zai)大(da)動(dong)(dong)量(liang)(liang)(liang)轉移(yi)(yi)大(da)下(對(dui)應(ying)于(yu)(yu)布(bu)里(li)淵(yuan)(yuan)區(qu)(qu)邊(bian)界(jie)(jie)(jie)(jie)(jie)(jie)的(de)(de)(de)(de)(de)(de)(de)ZO)的(de)(de)(de)(de)(de)(de)(de)離域(yu)(yu)(yu)范圍只有(you)(you)大(da)約(yue)1.66納米(mi)。通過(guo)分(fen)析，他們(men)認為(wei)(wei)(wei)(wei)是(shi)(shi)同(tong)(tong)位(wei)素(su)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)的(de)(de)(de)(de)(de)(de)(de)不同(tong)(tong)振(zhen)(zhen)幅導致了(le)(le)振(zhen)(zhen)動(dong)(dong)偶極(ji)子(zi)(zi)(zi)(zi)(zi)(zi)大(da)小的(de)(de)(de)(de)(de)(de)(de)差異，從(cong)而引起界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)處存在(zai)(zai)(zai)(zai)一定(ding)(ding)的(de)(de)(de)(de)(de)(de)(de)電(dian)荷積累。這(zhe)(zhe)(zhe)些電(dian)荷通過(guo)電(dian)聲(sheng)(sheng)(sheng)(sheng)耦(ou)合效(xiao)應(ying)使得聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)離域(yu)(yu)(yu)化，并且積累的(de)(de)(de)(de)(de)(de)(de)電(dian)荷密度與動(dong)(dong)量(liang)(liang)(liang)轉移(yi)(yi)相關，這(zhe)(zhe)(zhe)也解釋了(le)(le)動(dong)(dong)量(liang)(liang)(liang)依(yi)賴(lai)的(de)(de)(de)(de)(de)(de)(de)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)離域(yu)(yu)(yu)行(xing)為(wei)(wei)(wei)(wei)。他們(men)對(dui)比(bi)了(le)(le)同(tong)(tong)位(wei)素(su)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)的(de)(de)(de)(de)(de)(de)(de)面(mian)(mian)(mian)(mian)內(nei)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)，發(fa)現并沒有(you)(you)明(ming)顯的(de)(de)(de)(de)(de)(de)(de)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)離域(yu)(yu)(yu)行(xing)為(wei)(wei)(wei)(wei)，其界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)過(guo)渡區(qu)(qu)域(yu)(yu)(yu)只有(you)(you)大(da)約(yue)一個單胞厚(約(yue)0.34納米(mi))，這(zhe)(zhe)(zhe)是(shi)(shi)因為(wei)(wei)(wei)(wei)面(mian)(mian)(mian)(mian)內(nei)晶(jing)格振(zhen)(zhen)動(dong)(dong)不會在(zai)(zai)(zai)(zai)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)聚集電(dian)荷。此(ci)外(wai)，他們(men)對(dui)比(bi)了(le)(le)普(pu)通的(de)(de)(de)(de)(de)(de)(de)石墨烯-氮化硼(peng)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)，也沒有(you)(you)觀察到聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)離域(yu)(yu)(yu)行(xing)為(wei)(wei)(wei)(wei)。這(zhe)(zhe)(zhe)些研究結果都自洽地(di)支持同(tong)(tong)位(wei)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)存在(zai)(zai)(zai)(zai)由(you)(you)振(zhen)(zhen)動(dong)(dong)偶極(ji)子(zi)(zi)(zi)(zi)(zi)(zi)導致的(de)(de)(de)(de)(de)(de)(de)電(dian)荷效(xiao)應(ying)。他們(men)進一步發(fa)現，這(zhe)(zhe)(zhe)兩種ZO模式在(zai)(zai)(zai)(zai)原(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)層之間(jian)也有(you)(you)不同(tong)(tong)的(de)(de)(de)(de)(de)(de)(de)變(bian)化。由(you)(you)于(yu)(yu)聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)色散在(zai)(zai)(zai)(zai)布(bu)里(li)淵(yuan)(yuan)區(qu)(qu)邊(bian)界(jie)(jie)(jie)(jie)(jie)(jie)相對(dui)中(zhong)心(xin)(xin)(xin)是(shi)(shi)較為(wei)(wei)(wei)(wei)平(ping)坦的(de)(de)(de)(de)(de)(de)(de)，因此(ci)邊(bian)界(jie)(jie)(jie)(jie)(jie)(jie)的(de)(de)(de)(de)(de)(de)(de)ZO聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)能量(liang)(liang)(liang)相對(dui)來說對(dui)位(wei)置(zhi)變(bian)化不太敏感。此(ci)外(wai)，在(zai)(zai)(zai)(zai)從(cong)h-10BN層到h-11BN層的(de)(de)(de)(de)(de)(de)(de)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)上(shang)，ZO聲(sheng)(sheng)(sheng)(sheng)子(zi)(zi)(zi)(zi)(zi)(zi)的(de)(de)(de)(de)(de)(de)(de)能量(liang)(liang)(liang)都是(shi)(shi)首先上(shang)升，然后迅速下降(jiang)。這(zhe)(zhe)(zhe)些復雜的(de)(de)(de)(de)(de)(de)(de)行(xing)為(wei)(wei)(wei)(wei)可以(yi)通過(guo)結合微分(fen)散射截面(mian)(mian)(mian)(mian)和(he)界(jie)(jie)(jie)(jie)(jie)(jie)面(mian)(mian)(mian)(mian)上(shang)原(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)質量(liang)(liang)(liang)的(de)(de)(de)(de)(de)(de)(de)變(bian)化來定(ding)(ding)性(xing)地(di)理(li)解。

　　考慮到聲子模(mo)式在同(tong)位(wei)素(su)界(jie)面(mian)的(de)(de)動(dong)量依賴的(de)(de)離(li)域行為(wei)、電(dian)聲耦合效(xiao)應可能(neng)會影響(xiang)局域熱輸運和電(dian)輸運過程，因此這(zhe)些發現為(wei)我們理解天然(ran)材(cai)料中的(de)(de)同(tong)位(wei)素(su)效(xiao)應提供了(le)一個全新的(de)(de)角度，并為(wei)通過同(tong)位(wei)素(su)工(gong)程設計新的(de)(de)功能(neng)提供了(le)新的(de)(de)線索。這(zhe)些結果(guo)也表(biao)明具有原(yuan)子級的(de)(de)空間(jian)分辨(bian)和動(dong)量分辨(bian)能(neng)力的(de)(de)電(dian)鏡電(dian)子能(neng)量損(sun)失譜(pu)技術在探測(ce)原(yuan)子核量子效(xiao)應(包括同(tong)位(wei)素(su)效(xiao)應)方(fang)面(mian)的(de)(de)巨大潛力。

　　h-10BN/h-11BN界(jie)(jie)(jie)面(mian)處ZO模(mo)(mo)式(shi)的(de)(de)原子(zi)分(fen)辨(bian)分(fen)析。(a) h-10BN/h-11BN界(jie)(jie)(jie)面(mian)的(de)(de)HAADF圖像(b) 對應的(de)(de)電子(zi)能(neng)量損失(shi)譜數(shu)據，以及相應第一性(xing)原理計算結果(c) 計算得到的(de)(de)h-10BN/h-11BN界(jie)(jie)(jie)面(mian)附近典(dian)型聲子(zi)模(mo)(mo)式(shi)的(de)(de)空間(jian)分(fen)布(d) ZO模(mo)(mo)式(shi)在界(jie)(jie)(jie)面(mian)附近的(de)(de)能(neng)量變化。黑(hei)點是(shi)每個(ge)譜的(de)(de)擬合聲子(zi)能(neng)量，標準差如(ru)紅色和藍色陰影所示。橙色和青色實線(xian)是(shi)通過(guo)Logistic函數(shu)擬合黑(hei)點數(shu)據得到的(de)(de)，代(dai)表布里淵區中(zhong)心(xin)和邊界(jie)(jie)(jie)聲子(zi)的(de)(de)離(li)域(yu)范圍分(fen)別(bie)為3.44納米和1.66納米(e)振動偶極子(zi)和由(you)界(jie)(jie)(jie)面(mian)處原子(zi)位移的(de)(de)不連續(xu)性(xing)引起(qi)的(de)(de)累積束縛電荷的(de)(de)示意圖

　　北京大(da)學(xue)(xue)前沿交叉學(xue)(xue)科(ke)研(yan)究(jiu)(jiu)院2017級(ji)(ji)博士(shi)(shi)研(yan)究(jiu)(jiu)生李(li)寧(導師是(shi)王恩哥)、物理學(xue)(xue)院量(liang)子(zi)材料(liao)科(ke)學(xue)(xue)中心2018級(ji)(ji)博士(shi)(shi)研(yan)究(jiu)(jiu)生時若晨、材料(liao)科(ke)學(xue)(xue)與工程(cheng)學(xue)(xue)院2018級(ji)(ji)博士(shi)(shi)研(yan)究(jiu)(jiu)生李(li)貽非(fei)為文章共同第一作(zuo)者，高鵬(peng)、劉磊、陳(chen)基、王恩哥為論文通訊(xun)作(zuo)者。上述(shu)研(yan)究(jiu)(jiu)工作(zuo)得(de)到(dao)國家重點研(yan)發計劃、國家自然(ran)科(ke)學(xue)(xue)基金、北京大(da)學(xue)(xue)電子(zi)顯(xian)微鏡實驗室、北京大(da)學(xue)(xue)高性能計算平(ping)臺(tai)、量(liang)子(zi)物質科(ke)學(xue)(xue)協同創新中心、輕元(yuan)素量(liang)子(zi)材料(liao)交叉平(ping)臺(tai)等(deng)支持。