Magento 2 – Catalog Fulltext Search by Two Letters

Yes,in this possible .You need to use Custom route in this case.

Create a custom route .

• http://inchoo.net/magento-2/routing-in-magento-2/
• Magento2 adding dynamic route name

On custom route you can need it to katalog/resultate as controller as

Create di.xml

Create di.xml for define custom route in configuration

<?xml version="1.0"?>
<!--
/**
 * Copyright © 2017 amitbera.com
 * created by Amit Bera(dev.amitbera@gmail.com)
 * Module is created for Custom Router demonstration
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
    <type name="Magento\Framework\App\RouterList">
        <arguments>
            <argument name="routerList" xsi:type="array">
                <item name="katalog" xsi:type="array">
                    <item name="class" xsi:type="string">[Vendorname]\[Modulename]\Controller\Router</item>
                    <item name="disable" xsi:type="boolean">false</item>
                    <item name="sortOrder" xsi:type="string">22</item>
                </item>
            </argument>
        </arguments>
    </type>
</config>

route file:

<?php
namespace [Vendorname]\[Modulename]\Controller;


class Router implements \Magento\Framework\App\RouterInterface
{
    /**
     * @var \Magento\Framework\App\ActionFactory
     */
    protected $actionFactory;

    /**
     * Response
     *
     * @var \Magento\Framework\App\ResponseInterface
     */
    protected $_response;

    /**
     * @param \Magento\Framework\App\ActionFactory $actionFactory
     * @param \Magento\Framework\App\ResponseInterface $response
     */
    public function __construct(
        \Magento\Framework\App\ActionFactory $actionFactory,
        \Magento\Framework\App\ResponseInterface $response
    ) {
        $this->actionFactory = $actionFactory;
        $this->_response = $response;
    }

    /**
     * Validate and Match
     *
     * @param \Magento\Framework\App\RequestInterface $request
     * @return bool
     */
    public function match(\Magento\Framework\App\RequestInterface $request)
    {
        /*
         * We will search katalog/resultater and “exampletocms” words and make forward depend on word
         * -katalog/resultate will set front name to catalogsearch, controller path to result and action to index
         */
        $identifier = trim($request->getPathInfo(), '/');
        if(strpos($identifier, 'katalog/resultater') !== false) {

            $request->setModuleName('catalogsearch')->setControllerName('result')->setActionName('index');

        } else {
            //There is no match
            return;
        }

        /*
         * We have match and now we will forward action
         */
        return $this->actionFactory->create(
            'Magento\Framework\App\Action\Forward',
            ['request' => $request]
        );
    }
}

Try below code its work for me:

$this->filterBuilder->setField('search_term');
$this->filterBuilder->setValue('wat');
$this->searchCriteriaBuilder->addFilter($this->filterBuilder->create());
$searchCriteria = $this->searchCriteriaBuilder->create();
$searchCriteria->setRequestName("quick_search_container");
$this->searchResult = $this->searchInterface->search($searchCriteria);

//Create Temp table for store result 
$temporaryStorage = $this->temporaryStorageFactory->create();
$table = $temporaryStorage->storeApiDocuments($this->searchResult->getItems());        
$productCollection = $this->_productCollectionFactory->create();
$productCollection->getSelect()->joinInner(
       ['search_result' => $table->getName()],
       'e.entity_id = search_result.' . TemporaryStorage::FIELD_ENTITY_ID,
       []
);


// Classes need to load

use Magento\Search\Api\SearchInterface;  //$this->searchInterface
use Magento\Framework\Search\Adapter\Mysql\TemporaryStorageFactory; // $this->temporaryStorageFactory
use Magento\Framework\Api\Search\SearchCriteriaBuilder; // $this->searchCriteriaBuilder
use Magento\Framework\Search\Adapter\Mysql\TemporaryStorage; //TemporaryStorage