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,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費米子等。本論文主要介紹基于我們87Rb玻色子和40K費米子的超冷原子系統(tǒng)上最近所做的一些工作：在超冷費米氣體中研究了射頻場對Feshbach共振的散射控制；自旋—軌道耦合對Feshbach分子的解離效應(yīng)做了實驗和理論研究；在簡并費米氣體中首先實現(xiàn)了二維的人造自旋—軌道耦合；在二維自旋—軌道耦合的費米氣體中觀測打開拓樸能隙并做了相應(yīng)的研究。對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—軌道耦合做了簡單介紹；并對自旋—軌道耦合中的拉曼耦合強度做一個詳細的理論描述；為了在實驗中選擇一個合適的參數(shù),實驗研究了拉曼光波長和外部磁場對自旋—軌道耦合的耦強度的影響。實驗研究了超冷費米氣體中磁場Feshbach共振的射頻場調(diào)節(jié)控制。通過磁場Feshbach共振技術(shù),掃描磁場產(chǎn)生弱束縛的Feshbach分子,改變的射頻場頻率,觀測基態(tài)Feshbach分子到基態(tài)深束縛分子的能級躍遷,觀測到了三個束縛態(tài)到束縛態(tài)的共振躍遷。固定射頻場在某個能級躍遷的附近,測量了原子數(shù)隨磁場的變化,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產(chǎn)生,重新得到一個存在射頻場時Feshabch共振的損耗輪廓。實驗表明可以采用外部射頻場,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的過渡區(qū)域提供了可能；在超冷費米氣體中,當存在自旋—軌道耦合時,我們在實驗上在不同的磁場、不同的耦合強度等條件下觀測了該效應(yīng)對Feshbach分子的解離效應(yīng),并分別對動量對Feshabch分子解離的重要性、依賴于失諧的分子解離效應(yīng)以及在解離過程中剩余的分子數(shù)進行了理論分析和數(shù)值計算。在超冷費米氣體中我們小組首次實現(xiàn)二維的人造自旋—軌道耦合,在理論上對二維自旋—軌道耦合進行分析和預(yù)測,在實驗中通過自旋注入的方式測量得到二維自旋—軌道耦合的能譜并且得到一個高度穩(wěn)定可控的狄拉克點,并且得到狄拉克在動量空間的運動軌跡�；谝呀�(jīng)實現(xiàn)的二維自旋—軌道耦合的超冷費米氣體,我們理論分析并設(shè)計了如何打開狄拉克點處能隙的簡單易行的實驗方案,并通過調(diào)節(jié)拉曼激光的偏振來實現(xiàn)該方案。實驗中測量得到該方案下綴飾態(tài)原子的能量—動量色散譜并對狄拉克點處的拓樸能隙進行了精確測量。
[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)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O469

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