發(fā)布時(shí)間：2018-05-13 13:50

  本文選題：二維自旋—軌道耦合 + Rashba型和Dresselhaus型自旋—軌道耦合��； 參考：《山西大學(xué)》2016年博士論文

【摘要】：近年來(lái),自旋—軌道耦合的超冷原子氣體引起了人們極大的興趣。利用自旋軌道耦合的超冷原子系統(tǒng)可以模擬研究許多與帶電粒子在電磁場(chǎng)中的物理行為相關(guān)的許多有趣的物理現(xiàn)象,如量子霍爾系統(tǒng)、自旋霍爾效應(yīng)、拓樸絕緣體、p-wave超導(dǎo)體以及Majorana費(fèi)米子等。本論文主要介紹基于我們87Rb玻色子和40K費(fèi)米子的超冷原子系統(tǒng)上最近所做的一些工作：在超冷費(fèi)米氣體中研究了射頻場(chǎng)對(duì)Feshbach共振的散射控制；自旋—軌道耦合對(duì)Feshbach分子的解離效應(yīng)做了實(shí)驗(yàn)和理論研究；在簡(jiǎn)并費(fèi)米氣體中首先實(shí)現(xiàn)了二維的人造自旋—軌道耦合；在二維自旋—軌道耦合的費(fèi)米氣體中觀測(cè)打開(kāi)拓樸能隙并做了相應(yīng)的研究。對(duì)Rashba型和Dresselhaus型自旋—軌道耦合以及由該兩種類型等權(quán)疊加的拉曼光誘導(dǎo)產(chǎn)生的—維自旋—軌道耦合做了簡(jiǎn)單介紹；并對(duì)自旋—軌道耦合中的拉曼耦合強(qiáng)度做一個(gè)詳細(xì)的理論描述；為了在實(shí)驗(yàn)中選擇一個(gè)合適的參數(shù),實(shí)驗(yàn)研究了拉曼光波長(zhǎng)和外部磁場(chǎng)對(duì)自旋—軌道耦合的耦強(qiáng)度的影響。實(shí)驗(yàn)研究了超冷費(fèi)米氣體中磁場(chǎng)Feshbach共振的射頻場(chǎng)調(diào)節(jié)控制。通過(guò)磁場(chǎng)Feshbach共振技術(shù),掃描磁場(chǎng)產(chǎn)生弱束縛的Feshbach分子,改變的射頻場(chǎng)頻率,觀測(cè)基態(tài)Feshbach分子到基態(tài)深束縛分子的能級(jí)躍遷,觀測(cè)到了三個(gè)束縛態(tài)到束縛態(tài)的共振躍遷。固定射頻場(chǎng)在某個(gè)能級(jí)躍遷的附近,測(cè)量了原子數(shù)隨磁場(chǎng)的變化,在寬的Feshbach共振背景曲線上出現(xiàn)非常窄的損耗,非常窄的損耗是由射頻場(chǎng)產(chǎn)生,重新得到一個(gè)存在射頻場(chǎng)時(shí)Feshabch共振的損耗輪廓。實(shí)驗(yàn)表明可以采用外部射頻場(chǎng),可以調(diào)節(jié)Feshbach共振的散射特性,也就是調(diào)節(jié)原子之間的相互作用,該技術(shù)為操控BEC到BCS的過(guò)渡區(qū)域提供了可能；在超冷費(fèi)米氣體中,當(dāng)存在自旋—軌道耦合時(shí),我們?cè)趯?shí)驗(yàn)上在不同的磁場(chǎng)、不同的耦合強(qiáng)度等條件下觀測(cè)了該效應(yīng)對(duì)Feshbach分子的解離效應(yīng),并分別對(duì)動(dòng)量對(duì)Feshabch分子解離的重要性、依賴于失諧的分子解離效應(yīng)以及在解離過(guò)程中剩余的分子數(shù)進(jìn)行了理論分析和數(shù)值計(jì)算。在超冷費(fèi)米氣體中我們小組首次實(shí)現(xiàn)二維的人造自旋—軌道耦合,在理論上對(duì)二維自旋—軌道耦合進(jìn)行分析和預(yù)測(cè),在實(shí)驗(yàn)中通過(guò)自旋注入的方式測(cè)量得到二維自旋—軌道耦合的能譜并且得到一個(gè)高度穩(wěn)定可控的狄拉克點(diǎn),并且得到狄拉克在動(dòng)量空間的運(yùn)動(dòng)軌跡�；谝呀�(jīng)實(shí)現(xiàn)的二維自旋—軌道耦合的超冷費(fèi)米氣體,我們理論分析并設(shè)計(jì)了如何打開(kāi)狄拉克點(diǎn)處能隙的簡(jiǎn)單易行的實(shí)驗(yàn)方案,并通過(guò)調(diào)節(jié)拉曼激光的偏振來(lái)實(shí)現(xiàn)該方案。實(shí)驗(yàn)中測(cè)量得到該方案下綴飾態(tài)原子的能量—?jiǎng)恿可⒆V并對(duì)狄拉克點(diǎn)處的拓樸能隙進(jìn)行了精確測(cè)量。
[Abstract]:In recent years, supercooled atomic gases coupled with spin-orbit have attracted great interest. Many interesting physical phenomena related to the physical behavior of charged particles in electromagnetic fields, such as the quantum Hall system, the spin Hall effect, can be simulated by using a spin-orbit coupled supercooled atomic system. Topological insulators, p-wave superconductors and Majorana fermions. In this paper, we mainly introduce some recent works based on our 87Rb boson and 40K fermion supercooled atomic system: the scattering control of Feshbach resonance by RF field in ultra-cooled Fermi gas is studied; The spin orbital coupling has been used to study the dissociation effect of Feshbach molecule experimentally and theoretically, and the two dimensional artificial spin orbital coupling has been realized in degenerate Fermi gas. The topological energy gap is observed and studied in the two dimensional spin-orbit coupled Fermi gas. The spin-orbit coupling of Rashba type and Dresselhaus type and the spin-orbit coupling induced by Raman light induced by the two types of equal weight superposition are briefly introduced. In order to select a suitable parameter in the experiment, the effects of Raman wavelength and external magnetic field on the coupling strength of spin-orbit coupling are studied. The RF field control of magnetic field Feshbach resonance in supercooled Fermi gas is experimentally studied. By means of magnetic field Feshbach resonance technique, the weak bound Feshbach molecule is generated by scanning the magnetic field, the frequency of RF field is changed, the energy level transition from ground state Feshbach molecule to ground state deep bound molecule is observed, and the resonance transition from bound state to bound state is observed. The change of atomic number with magnetic field has been measured in the vicinity of a certain energy level transition in a fixed radio frequency field. The very narrow loss appears on the wide Feshbach resonance background curve, and the very narrow loss is generated by the radio frequency field. A loss profile of Feshabch resonance in the presence of RF field is obtained again. The experimental results show that the external RF field can be used to adjust the scattering characteristics of Feshbach resonance, that is, the interaction between atoms. This technique makes it possible to control the transition region between BEC and BCS. In the presence of spin-orbit coupling, we have experimentally observed the dissociation effect of this effect on Feshbach molecules under different magnetic fields and different coupling intensities, and the importance of momentum to the dissociation of Feshabch molecules, respectively. The molecular dissociation effect dependent on detuning and the number of molecules remaining in the dissociation process are theoretically analyzed and numerically calculated. In the supercooled Fermi gas, our team first realized the two dimensional spin orbit coupling, and theoretically analyzed and predicted the two dimensional spin orbit coupling. In the experiment, the energy spectrum of two dimensional spin-orbit coupling is measured by spin injection, and a highly stable and controllable Dirac point is obtained, and the motion trajectory of Dirac in momentum space is obtained. Based on the realized two-dimensional spin-orbit coupled super-cooled Fermi gas, we theoretically analyze and design a simple experimental scheme of how to open the energy gap at Dirac point, and realize this scheme by adjusting the polarization of Raman laser. The energy-momentum dispersion spectra of the decorated atoms under the scheme are measured and the topological energy gap at the Dirac point is accurately measured.
【學(xué)位授予單位】：山西大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O469

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